Uncle Doug You still have it Mr Doug, I always enjoy a good class or explanation and your videos are some of the best I have seen on you tube. I also enjoy your video on building the finger joined amp, a friend of mine and myself wanna build a custom cab and that is a delux explanation.
@@UncleDoug Completely off the subject of your video, but I can tell you from experience that the best teachers seem to be people that actually were in the industry that they try to teach about. So much more to be learned by experience than from the teacher that just knows the answers to the questions from the book. Four years of math from teachers in high school and the things that stuck with me and made sense were the ones taught by a teacher who was a contractor on the side, he showed how the math actually worked in the real world.
Thank you Uncle Doug. Definitely some "shocking" information ! I hope a lot of musicians, especially young ones starting bands see this very important information that you are providing. Most mics are isolated from the stand by the plastic mic clips (or holders), so I always touch the guitar strings to the mic itself, or I just touch the mic with my hand, with the other hand on the guitar strings, checking for any "tingle". Also make sure your mic stand has all of its rubber feet & are in good condition. If the feet are worn down to where the metal screws (that attach the feet to the metal base) are contacting the ground, then the entire mic stand is a path to ground. I've been zapped while holding my guitar & grabbing a mic stand. It was missing one of it's 3 rubber feet, so the metal base was touching the ground. Once I had a blue spark from the mic to my front tooth. It almost knocked me out, going right up through the tooth nerve hurt like hell. Not a good place to get shocked. Since then I check at every gig, especially since there's a different sound company & sound system at each gig.
Greeting, Brian, and thanks for your input on this subject. As a performing musician, your experiences and warnings are especially beneficial to others who face shock hazards with guitars, microphones, and stands. The shock to the front tooth story sent shivers up my spine..... :O
Barefoot on a summer day getting ready to jam in the garage in my high school days, I got the shock of my life from a sketchy amp. That amp speaker later caught fire during a rehearsal!
Thank you SO VERY MUCH. My 8 and 9 year old grandkids got into music this past year. I bought my granddaughter a Martin electric acoustic, mic & stand, and a small Fender practice amp. She wants to be a singer like her GrandMaMah who’s been performing since age 3. By age 5, her GrandMaMah was taught about this. EXTREMELY portant
Great explanation! You can blow yourself off stage pretty good with bad venue/equipment wiring. I've toured thru venues with artists, and measured 120V and 220V between a guitar and mic. Sometimes I'd find it myself during setup, other times one of my artists would get it during soundcheck. I encourage guitar players to invest in a quality wireless systems for their rigs if they're touring. For me, it's a wise investment, simply for the sake of keeping the artist out of the electrical circuit. Typically we keep a few channels of "disposable" wireless around in case we find ourselves doing shows in the rain. Throw the wireless packs in a condom and play the show. Sweaty guitar players are typically harder on gear than the rain.
20 years ago, during a jam session in my friends garage, the bass player and I accidentally let our strings touch. He didnt have his fingers on the strings, but I did. I got a big shock and went blind and deaf for about 15 seconds and the reverb unit in my Ampeg head didnt work anymore after that. I assumed one of our amps was screwed up but I never investigated. I used that amp for years after and never had an issue, so I guess it was the old Kustom bass head
Very informative.. your videos are the most understandable and interesting I've been able to find on TH-cam about old tube amps. And by the way your drawing isn't too bad either, I love your sense of humor. Thanks...for passing on your knowledge and years of experience.
I can understand why a musician, faced with an audience expecting him to perform, would resort to drastic measures to keep his malfunctioning amp powered up.....but what a price to pay. This experience would definitely inspire me to have a few spare amps handy if I were ever in Mr. Harvey's shoes.
Learned my lesson tonight and im still a little shaken up from it. playing with headphones plugged into the amp (3 prong) hear some extra static so I go to turn off a small lamp hand gets close to the lamp (2 prong) and bam! muscles tighten up so hard I couldnt even let go of the damn thing until i moved far enough it unplugged and fell out of my hand. probably one of the scariest moment of my life.
Wow.....what a bad experience, PP. I had a similar one many years ago and actually experienced heart palpitations. We hope you resolve the wiring issue and never have a repeat of this scary event.
I'm glad you survived it, BT......240VAC will really get your attention. Although your experience was not amp related, I feel compelled to mention that when working on a live chassis, it's a good idea to keep one hand in your pocket....that way you can never accidentally complete a circuit from arm to arm (through your chest and heart) that might be fatal.
Someone else that works on amps told me that too. I have a Fender Champ 600 to fault find so will ensure I abide by that method. I'll probably also wear a nitrile glove on the other hand 👆. The amp gave up, it used to run rather hot for its mere 5W (output). Previous owner had someone install a modification kit consisting of an improved rectifier, DC heater supply and standby switch. I suspect they failed to follow the final part of the modification instructions (that I have obtained) that should check and adjust (resistors) to set the correct voltage to the tubes. So carefully checking that could be my starting point.
Thank you so much! I got shocked recently at home while playing guitar and this video helps my on my way to understand how all of this works and how to remedy the situation. Nice drawing by the way :)
Have you seen the video by "Woodeso's guitar mods?" This guy has his left hand on his strings than grabs an ungrounded metal lamp post and gets zapped. He broke loose by falling and knocking it loose from his hand. This goof ball doesn't even know why it happened and thought it was funny so he still has the video available to watch...you should probably give him a heads up and tell him about the death of Keith Relf from the yardbirds.
Thanks for this video, Doug. My personal philosophy is -- originality be damned, any piece of vintage equipment I have gets a proper grounded plug. I learned my lesson many years ago when I had the "ground" switch flipped the wrong way and high-fived my bandmate after a particularly awesome rendition of Into The Void.
Jason Thorpe I understand, Jason, and agree that any equipment that will be used commercially definitely should have a grounded, three-wire cord. On pristine, vintage equipment, receiving limited use at home and in controlled conditions, I tend to favor originality, as long as the precautions I have described are followed.
Been there. For me, the show came to a stop until things were sorted out. In dive bars where things were too weird, we either did a straight acoustic show or we cancelled.
Hello! This video has been really helpful! I wanted to tell you about the problem that i've been having with my equipment. Maybe you could help me find out what seems to be the malfunction.. Recently i bought a brand new electric guitar and an used 10w amp (this because of budget issues haha) and i've been experiencing electric shocks whenever I touch the power switch of the amp. This amplifier has the three plugs. What i've noticed in these couple of days since I bought all of this equipment, is that I get the shock when I touch the amp (while is connected to an extension where I also connect my PC, the monitor and desk lamp) at the same time that i'm grabbing my guitar.. I plugged the amp directly to a socket and did'nt receive any shock that way.. but in reality i'm a little afraid to confirm it again.. What are your thoughts? I'd really appreciate if you could help because this has been kind of a bummer
Does the extension cord have 3 wires.....or two? Most have only two and do not provide any grounding capability. If no shocks occur when you plug the amp directly into the wall, then this is the ONLY way it should be plugged. I have no idea what type of amp this is, but it seems to have internal grounding issues that may need to be addressed.
@@UncleDoug the extension i've been using has three wires and this has been happening only with the Amp. I have also connected my pc and monitor to this extension and never gave me any problem. And the Amp I bought is a Vox pathfinder 10, wich i got from a local music store in very good conditions and used!
@@gabo_caruso If there is no shock when the amp is plugged into the wall, but there is a shock when you use an extension cord, then it would seem that the cord, regardless of how many wires it seems to have, must be the cause. The PC has an insulated body and would not be a reliable comparison.
@@UncleDoug Today I tried both ways: Amp connected to the extension and then connected to the wall. And in both ways I felt current coming out of the amp's chassis (doesn't hurt or anything), specially when I put my finger over the power switch. Also happens with or without the guitar plugged to the amp.. There must be something wrong inside the amp i guess.. But the weirdest thing is that in the music shop, this didn't happened at all.. It's happening where I live. Anyways, your responses have been very helpful! I really appreciate it!
Hi uncle Doug about 35 years ago I experienced this. thank you for putting this out to musicians and techs,I was in our studio with our singer the whole rm was covered with carpet summer day hot as hell sweating my guitar strings welded to the mic stand. my lips touch my mic to sing and boom blue ⚡️ sparks I tried to scream nothing came out I was picked up an thrown against a old wooden chair that broke to pieces my singer told me what happened when I came to the polarity on his PA and my amp had changed. I didn't feel so good and didn't play guitar for a week . I guess I'm Lucky to be alive ...thank you for your top notch videos I love em...
You're welcome, LL. We're glad you survived this ordeal and took the time to warn others about the shock hazards associated with polarity differences in equipment.
Yes, Uncle Doug. I had the mic thing happen. Had my Les Paul Gold Top plugged into my 100 watt Ampeg V4. I boldly stepped up to the mic to sing, when out of nowhere, a purple caterpillar appeared and jumped from the mic to my upper lip. It bit me and vanished just as suddenly. I started singing the song a cadence later, and did so from six inches away. Stuff like this used to happen all the time, and we usually held our plugged in guitar in one hand and smacked at the mic stand and each other to check for a current differential. It was the poor kid's volt meter. By the way, heard Rusty's guitar solo on one of your other videos. It was masterful.
Addy Adderson Greetings, Addy. Thanks for sharing your "shocking" experience with mixed polarity in musical equipment. The "poor kid's volt meter" analogy was great :) Rusty sends his regards and appreciation for your kind appraisal of his musical skills :) ^. .^
I'll never forget at a practice in an old warehouse in jacksonvile florida got an arc from the mic and the lights dimmed, ouch! I hate when that happens
Uncle Doug says: "All you do is this, take the guitar, and touch the strings to the microphone stand, and watch what happens. If theres a big blue arc (it looks like an arc welder just fired up), do not under any circumstances come up here and start singing into this microphone." - Thats some good advice right there! Thank You, great video!
Thanks so much, Matt.....glad you liked it. I got a little hyperbolic, but it's a reliable, simple test. Even tiny sparks indicate that a serious problem exists and has to be corrected. Thanks for watching and posting your comment :)
Anything you say is 100% correct and relevant; however I prefer to talk intensity and resistance, which are easier to understand for most people: a) the danger is current intensity for the human body: 30 mA, across the chest, cause muscles tetanization (heart and lungs blocking, inducing terminal syncopes and rapid brain melting) b) the human body resistance varies between 100 ohms and 1000 ohms (depending of your health condition , weariness and stomach content) * most deadly electric shocks occur between 11-12 am and 17-18 pm when workers are hungry (official accident stats in french data base) So a tension of 0.03x1000 = 30 V is potentially lethal (maximum allowed in High schools and College physics labs, in France) So ALWAYS use an amp with a 3 wire cord, grounding the chassis and the metal parts on your guitar... Please update your vintage tube amps (discard the cloth woven wires and ignore the self proclaimed "tube gurus" opinions: it might save your life, at ultra low cost...) In continental Europe, we have 220 to 240 V power outlets : it's not forgiving! 240 V /1000 ohms = 240 mA = a one way lane to BBQ heaven 240 V / 100 ohms = 2.4 A = the frying pan great video as always... BS free speech, coming from someone who knows what he's talkin about
I wouldn't think that the field coil of the speaker would be a hazard, but if one shocked you, then maybe so in the case of this unusual amplifier. You can test it with a voltmeter like I do in the Death Capacitor video. Connect one lead of the voltmeter to a good ground and then touch the other lead to metal parts of your amp when it is plugged in and turned on. If there is any shock hazard, the meter will give a reading of the amount of voltage present in the chassis and speaker.
Hello again! This is a good video for many players to watch...I try to explain this to many guitarists who's amps I repair, but they look at me funny :) I tend to explain it tech terms and sometimes I don't realize it and think I'm talking to another tech...But this video explains it in simple comprehensive terms for the non-tech person...another great video! :)
You may have saved my life by making this video...I have zapped my lips on mics many times...and shocked myself on my amp's chassis several times in the past...my amp is circa 80's point to point -100w with 3 prongs but I suspect I have a grounding issue...I am going to check things out with a volt meter as you suggest. Incidentally, I once saw a video of Hendrix rubbing his guitar against his mic stand...perhaps more as a precautionary, rather than artistic measure.
Bob Flint If the video prevents you from receiving a serious shock, Bob, then it truly served its purpose. You really need to investigate the cause of the shocks you have been receiving. Bear in mind that the fault may well be in equipment other than your own. If your amp and guitar strings are properly grounded, then you become grounded when you touch them, and electricity from any improperly wired equipment you come in contact with will try to pass through you to that ground. Jimi was checking to see if his (grounded) strings were attracting an electrical spark from the mic stand before he came in contact with it. It's a standard test, as mentioned in the video, and sort of a last resort. A little portable voltmeter can do a better job of assessing any potential between pieces of equipment and can save your life. Best of luck.
With that being said, I think I've discovered something that I thought was just a fashion statement or that looked cool. Especially in the sixties and seventies when amps and equipment didn't probably have three prong electrical cords, bands would have all these beautiful rugs on the stage that look very cool and even today, well maybe this helped them the musicians from getting electrical shock all the while looking so cool when the Greatful Dead played.
Rugs and rubber mats would be a good precaution, Ron, particularly if the stage was metal. If the performance was outside and it rained, however, all bets are off :)
Yep that explains it! I was bare footed every time on the polished concrete floor of my garage! Got shocks from the strings after playing my Strat appx 10 mins. I was using a Vox mini practice amp with a 9V DC adaptor. Thanks for the explanation.
lanthaniated1, Hmm, now how could this happen? the only way I can see that you would get shocks from a 9 volt wall wart adapter is if it was seriously defective or seriously designed him properly. Perhaps it uses a transformerless "switching" power supply? and/ or was additionally defective? a different wall wart adapter might cure this problem. here's a hint, if the 9 volt adapter seems very lightweight like it's all plastic almost, it's probably a switching Supply. Anything with an actual Transformer is going to be a bit heavier. The switching supply will have some inductor coils in it but usually it's not very big on the copper wire content nor does it have the steel core necessary for a Transformer.
I'm a little confused by the question, AR, but the word "potential" means a difference in electrical charge between two objects or locations. If a connection is made between them, then a current will flow from the one with too many electrons to the one with too few. If a potential exists between an amp chassis and ground, and if you touch both, an electric current will flow through you from the chassis to ground.
🔥 this is a very very overlooked subject and I'll never forget the shock I got off my 1970 200 watt Marshall major because of that pin plug for the ohm adjustment bounced out was not a good scenario
Great video. Had a band mate get a shock off a mic stand once, and this is in the UK where everything should be ground wired. He played on against my advice, but thankfully survived!
+Giath Majstorovic I've never had any venue ask for proof that gear was PAT tested, and we've played a lot including some medium sized festivals etc. In any case this was the venue's gear so wouldn't have helped!
makes perfect sense - will do the test before the amp is serviced and then again, to see if there has a hazard from the field coil or any other parts and then after as well. i should be sure then. thank you for the great videos you've been making - they way. it is a great library of historical amps and also very educating. with tis words i'll say "greetings ;)"
First off all , Thank you for sharing your knowledge and taking up your time for doing all of the Topics on Tube Amplifiers . We spend all the Money thousands of Dollars /Euros or what ever, to buy the fanciest Gear , Amps , but most of us we don't have the Money to buy a Power Source for our Amps to provide us and our Amps with the needed and save Electricity where ever we go, this Power source must have the capability to shut off the Power as soon you have a ground loop or other electric malfunctions, or in the case some of our equipment catches Water , like a residual current circuit Breaker I hope this is the right Term for this. Here in Norway are existing very old Houses where the 240 V come in 2 wires 120 Volts each , a I forget how they go to ground if it existed . This should never occur this times but you never know . And today the Ground Lift switch and the Death cap are forbidden in Europe , because those devices led to many injuries or deaths. One thing , I don't do Patreon so if you let me know how I can support your Chanel in another way , please use my e-mail for this .
Doug - always great work. You are very appreciated. Just a couple of thoughts: The microphone is usually attached to the stand with a plastic or hard rubber clip. This would pretty much isolate the mic chassis ground from the stand. Also, many mic stands themselves have rubber feet to keep them off ground. In that case, touching the guitar strings to the mic stand won't do anything, other than charge the stand.
Thanks, Paul. Rubber feet or not, if the microphone and/or stand have/has a polarity opposite that of the guitar strings, a potential will exist.....as will a shock hazard. The potential between microphone and ground is immaterial. All that matters is whether, due to improper wiring and mixed polarity, a potential exists between any two pieces of equipment. This can be prevented by the proper installation of polarized, 3-wire, chassis-grounding power cords.
Thanks, F86. I just watched a video of his and couldn't resist. I probably should have included a cigarette on his lip too, just to make it more realistic, but the smoke might have made it look like he was being electrocuted ;)
Hey Rusty, hey Doug. There is one thing that imho is very important to mention, when it comes to discussing the danger of electric shocks on guitar amps... I´m talking about the condition of your mains plug... I´ve seen many in very bad shape (always the european style, of course) - sometimes the plugs were not even properly fixed to the outer shell of the cable... If the ground-wire gets ripped off inside the plug and touches the pin that carries the 120V (in our case: 230V) it becomes very dangerous...!!! If you´re playing your guitar in this moment, there will be hardly any chance to get your fingers off the strings anymore, as your muscles will be convulsing... Dogs are more safe, as they cannot put their paws around a guitar neck and they do have some additional fur-insulation...!
A good point, Sal. Plugs, especially on amps carried to and from performances, can get trampled and damaged, so their integrity must be checked regularly. Rusty says that he has been shocked several times during gigs, but a couple shots of bourbon (both before and after the shock) seemed to make his paws feel a whole lot better :)
This kinda explains how i got shocked. About a year ago i bought a sears catalog amp from the 60s and i had it cranked. Went to touch another amp of mine that was on and immediately i got shocked like hell. Even had a giant red streak going from my arm to my chest
You're lucky you survived, G&G. The electrical path passed near or through your heart......the worst possible scenario. Please heed the warnings in the video and stay safe.
An outlet checker is cheap, and provides some clue if the condo or club was wired right. Once, I was resusing an industrial outlet strip, when I noticed that Hot was wired on the larger blade of the plug. I opened it, it and rewired it. ~ Perhaps for amps where the original 2-prong unpolarized cord remains in play, perhaps a sticker or a paint spot could mark which plug blade is neutral. ~ I used to disconnect the bridge wire from my guitars. I suspect that they had hoped that the strings might shield the pickups, and having the strings grounded might have helped. (Still the plug, jack, and pickups might be hot, but anyway....) Well, perhaps a compromise could be made. I got the idea from anti-static wrist straps. They have a 1 meg-ohm resistor in them to limit the current. Perhaps a resistor such as a 1k-100k ohm could be wired in series with the bridge wire, then the strings can still be part of the shielding solution, but at least the current is limited, and the voltage is much lower. Thanks for the videos.
The main concern, from a shock standpoint, has to do with the AC part of the circuit, since "ground" for that circuit is just about everywhere.....pipes, cement floors, door frames, etc. The DC circuit is restricted to the chassis and can kill you if you reach into the chassis and touch highly charged areas with both hands....but who does this, unless they are actually working on the amp? AC can get to the chassis through any short in the primary circuit between.........
You Sir are a great instructor. I just put my DMM across the chassis of my beloved two-prong plugged Kalamazoo Model One, got almost 4v, flipped the plug over and got 113v. I now know how to deal with it thanks! I owe you dinner at L&J
Thanks, Jeff. I'm glad the video was helpful, but please be careful with any amp that has potential within the chassis. Have you considered installing a polarized, 3-wire, chassis-grounding power cord ??
Thanks, Bobby. I agree with you re the three-wire grounded cord, especially if you are going to set up your equipment with other equipment of unknown polarity and grounding. As my old granny used to say, "It's always better to be safe than sorry."
Hi Doug. Love your channel...just a thought. all modern microphone clips are plastic so people won't get a boot off the stand but through the mic grille. so a better safety check would be to touch the strings to the mic before. as you say tonguing the microphone! Cheers from New Zealand
And by the way, my other amps work normally from the same outlet, and the amp is solid state. It also pops loudly when turned on, and it wasn't on when I got the shock. It also has a circuit breaker on the back of it, and I believe a fan inside of it, and is supposively 880 watts solid state (coliseum 880) thanks for the video
I've gotten the mic shock more times than i can remember. The worst was at this small club while using someone else's amp. It was old and rugged looking, plus the power situation was complete mystery. I just showed up in a hurry with my guitar and plugged in. The shock i received when i kissed that mic was so bad, it rendered me completely unable to process any thought for several seconds. I just stood there looking like some ancillary character from rick and morty. That stuff is no joke under certain circumstances, man. If it was any worse, i could've easily passed out.
I've been feeling the tingling sensation on my fingers everytime we jam and i once got shocked real bad(it scared the shit outta me and really painful) the time i accidentally took my foot off my footwear and stepped on the concrete, i had no explanation why,its always been a mystery but not anymore, this video explains it very well, it makes sense now, thanks,😄🙏🙏
Please be safe, LB. It really can kill you. Be sure you are insulated from concrete and that your equipment is properly grounded with 3-wire power cords.
Well that clears things up, really wish manufacturers would put stuff like this in users manuals for people that don't know that if you ground the microphone cabinet and your guitar amp isn't grounded you get shocked and there is a possibility you could die. From now on (as far as I know) I'm not gonna "reduce the hum" on my Alto 12 inch speaker by grounding it because it could be fatal. I live in Poland so the plugs don't have 3 prongs and therefore are not grounded, meaning my Vox AC30C2 isn't grounded, so that's that Also, got to get a windscreen for my mic to further reduce the risk
Are the sockets polarized, Hubert ? One tall slot and one short slot. In the U.S., the shorter slot is the "hot" lead. If they are, then it would be helpful if all your gear had polarized plugs.
11:35 FYI The microphone may be insulated from the stand by the plastic clip. You must touch the strings to the microphone itself while holding only the wood on your guitar.
I had a similar experience last summer playing a gig on the beach. Since it was warm, I took off my shoes and immediately started getting an alarming tingling feeling from my strings when standing on the sand. I was also having all sorts of buzzing problems with my amps and pedals and couldn't figure out what was going on. After the gig (successful despite the problems), I talked to my friend who is an amateur tube amp builder, and he explained grounding issues to me. Now all my gear is properly grounded with three-prong cables, and I always take good care of it. I discovered early on that missing ground could result in buzz, so I was quite puzzled. Then I remembered that the venue owner connected our stage with a cheap Chinese 30m extension cord which was buried under the sand... then it clicked 🙂 Moral of the story: Your wall power source might not be grounded, so no matter what you do, safety measures still apply.
Thanks for the very informative input, G. You're right that all wall receptacles should be tested for proper wiring. After living in my house for almost 30 years, I discovered that a receptacle in my amp room was wired backwards (black to white).
@@UncleDoug Ah, that's a bummer! Same here in Italy - I talked to another musician and they said grounding issues are pretty common at small venues. Apparently, the only workaround they knew of was sticking a metal pole in the ground and connecting it to some metal part of the equipment to create a makeshift ground. I'm wondering if that's safe and if there are better ways to test the receptacles on-site?
@@galacticx738 Receptacle testers are readily available at Home Supply stores or on Ebay. The metal pole in the ground is a classic way to provide earth ground. Be sure the ground is damp around the pole.
I like making radios and amplifiers. Always with a 'cold' chassis of course. Old radio sets can be pretty dubious where safety is concerned. The old UK standards allowed a 2 pin plug which could insert the wrong way, like the American plug. I have had cheap radios without isolated chassis & only a single-pole mains switch on the 'cold' wire. Pretty horrific, even though standards were different back in the day. The stuff I make is waaay better.
I have managed to electrocute myself. One time only. I landed on my bed so damn hard the frame cracked. It is plated with some aluminum sheet to this day. The Grim Reaper ain't getting another chance, no siree. I make sure the damn plug is out of the socket. An old radio guy told me a good peice of advice: "Keep one hand in your pocket" Obviously if the charge flowed up one arm and the other was the ground the electricity is going to mess up the function of your heart. Game Over!
I have survived a dose of 230V & lived to tell the tale. Broke my friggin bed frame tho when I landed. I had to plate it with aluminum I was keeping to make a chassis. Never again! Not only do I pull the plug I make sure it is plainly visible to me.
It was a helpful video.Last month I was playing wid my guitar I felt a slight shock at the 3 fret.I thought it was crackling of my finger bone but later on it was occuring again and again.From that day onwards I make sure that I wear rubber shoes while playing guitar
Harshad Shriyan Harshad, if you're getting shocked by your guitar strings, you need to check the ground wire on your amp chassis and ensure that your electrical outlets are properly wired and provide a good, solid ground. Ignoring this problem might lead to worse shocks and even bodily harm.
Regarding what you said at 2:38: If I understand this correctly, the electrons can flow into your body through the cable shielding, but not through the cable itself. Is this because of the high impedance of the cable (typically reater than 10,000 ohms) delivering the signal to the pickups? If so, what would happen if you touched the pickups, or just the guitar cable? For example: I have never heard of anyone getting shocked from touching a tip of a guitar cable with the other end plugged into the amp. Thank you for the great video!
Matt, the reason the shielding is implicated (and not the signal wire) is that it is connected to the amp chassis (the source of the shock hazard) and the parts of the guitar that you come in contact with. The signal wire is not. If it were, and this is something that many people have encountered with incorrectly wired jacks, there would be a loud hum from the speaker because the metal parts incorrectly connected to the signal wire would act as an antenna to extraneous noise. The loud hum would force you to correct the incorrect wiring. With correctly wired jacks, the tip of a guitar cable cannot carry any harmful voltage or current.....it connects to the grid of the first pre-amp tube where no such voltage or current exist.
I just recently found your channel, that's another great video uncle Doug! you also have great drawing skills, who wants fancy screen graphics when you can produce this kind of artwork !
Apologies in advance for the length and details of the following post, but here are some "shocking" scenarios I have encountered in person. 1) I have a Dan Electro amp with a top-mounted preamp that includes a couple of tubes as well as the volume and tone controls, with the main amplifier chassis on the bottom of the amp facing the rear and incorporating a pair of 6 L 6s and the 5 y 3 rectifier and a driver tube. There is a wiring harness of four or five wires as I recall going from the amp chassis up to the top mounted preamp, and there's also a shielded RCA cable with bare metal shield, uninsulated, coming down to the amplifier from the preamp to carry the audio signal. As I was working on it and trying to track down some intermittent noises, I had unplugged the RCA cable joining the preamp and an amp to see if the noise problems still existed with the preamp audio drive disconnected. At some point I went to plug that RCA cable back into the amplifier chassis while it was turned on, with my right hand leaning or braced against the amp chassis , and my left hand grasping the unshielded RCA jack and cable. Apparently, the preamp had no power supply ground, much less audio ground, included in the wiring harness, and instead the electrical ground was being made by that RCA cable being plugged into the amp. As I worked on the amplifier I unwittingly became the ground path between the top mounted preamp in the bottom mounted amplifier, and because the preamp had high voltage running to it to feed the preamp tubes*, and I had already added a grounded cord to the amplifier chassis, I got one heck of a shock. Needless to say, I added a separate top to bottom ground wire to permanently connect the two pieces electrically, and I disconnected the RCA shield on one end because it was no longer needed as a ground, and also to prevent ground loops. Anybody who has a vintage amp with a 2 chassis set-up, not just an actual top mounted preamp incorporating tubes and circuitry, but perhaps just a passive input jack panel with volume and tone on it, should really check the grounding scheme for safety, especially if there is a tube or tubes in the top half of the system, and also to see if the shielding of the audio cables is being used as the main and only ground in between the top input jack panel and the amplifier at the bottom of the cabinet. I worked on a very cool old Masco amp a while ago, I think it was a 120n or similar, and although the top-mounted input panel did not have any tubes in it, it hummed really badly until I ran a ground wire from top to bottom and disconnected the shields of the audio cables at the top panel by the volume and tone control. Perhaps the least safe design of a consumer electronic product that I ever saw was an old compact but heavy Califone record player, with a completely all- metal silver grey chassis and a built-in speaker, that was probably meant for school usage. This thing was a transformerless amplifier that had a voltage doubler, or was it a tripler? that was fed directly off of the AC line cord !!!!!! It actually had an RCA black plate 6L 6gc run single-ended, and a fairly beefy output Transformer, and a single 12 ax7, but it didn't have a power transformer! I wonder how many children and teachers got a nasty surprise from one of those!? I have seen two of them, they were cool to steal the output transformers and tubes out of, but no way would I want anybody to use one nowadays! Not to mention that the tonearm probably weighed three or four pounds. you could probably plow a cornfield with the stylus pressure from that thing! *That particular Danelectro (can't remember the model number, I'll have to look it up) zapped me even harder then you might expect because it has an unusual design, whereby the series-wired filaments of two 12 ax7s are fed approximately 24 volts DC directly off the combined cathodes of the 6 L 6 output tubes, and the resistance of those (2) 12 x 7 filaments or heaters actually forms or comprises the "cathode resistor"! This is a variant of an old hifi trick that lowers noise because you would normally be "wasting" 20 or 30 volts across the cathode resistor for the output tubes, and sometimes you'll see an amplifier that has the cathode resistor and still uses that 20 something volts found at the output tube cathodes , above the cathode resistor to ground, to drive the heaters of a couple of with some clean DC voltage, but in this particular case they eliminated the cathode resistor entirely !!!! Anyway, the two 12 ax7 heaters are connected to the chassis of the top preamp on one end , but when I was fiddling with the amp those 12AX7 heaters temporarily didn't have a ground connection, which means that the output tubes didn't have a cathode to ground connection either, so the B+ voltage at the 6l6 plates was also present at the 6 L6 cathodes, and looking for a path to ground, which it found by passing through the cold low-resistance 12 ax7 heaters and through the RCA cable shield and through my arms and chest to the chassis. The upshot is that whatever the main B+ to the output tubes was, some 430 olts or so as I recall, I got virtually all of it !
Wow....a very informative and somewhat scary commentary, GU. Thanks for helping to impress viewers with the importance of electronic safety procedures.
You might think twice about getting that vintage gear off eBay or Reverb. I know for a fact older neighborhoods in the Northeast ( where I live) have some houses with two prong outlets with fuse boxes instead of breakers. Some people replace the two prong outlets with three and don’t ground them. I carry a wire tester that I use before I plug in my amp.
I have found that, if the chassis is HOT you can feel hum on the metal parts with the back of my hand. if there is hum then changing the direction of the two prong plug usually puts the chassis closer to ground..
Greetings, Dan. I can think of no reason why a properly wired chassis would be "hot". There are no direct connections between the primary circuit and the chassis, other than perhaps a leaky "Death Capacitor", which is rather uncommon. If the chassis is indeed energized, the source of the leakage should be detected and eliminated. Then, installing a 3-wire chassis-grounding power cord would eliminate the possibility of any further issues.
I have this same problem with a vintage open reel tape deck. I get a small shock when touching the chassis of the deck and a metal framed shelf. I plan to open up the deck and find the bad capacitor, and replace it. Before I use it anymore.
Greetings, MM. Your shocking problem may not be due to a capacitor, and it may be a health risk. Your best bet is to install a 3-wire power cord in this tape deck and be sure the green (ground) wire is securely attached to the chassis. Don't take chances with this.....it really needs to be done.
Uncle Doug I sent you a PM describing my problem in more detail. Including voltage measurements in several different situations. The shock is annoying but not lethal. I haven't tried grounding the chassis yet. Afraid it might damage my deck in this condition. Please read my PM and advise. Thank You.
I'm glad I play the electric guitar as a hobby at home with a USB Audio Interface to my computer using Guitar Rig 5. I never got shocked once, I always wear rubber sole shoes on the carpet in my room when I play. My hands sweat sometimes but that's never been an issue either. Also no, I don't have a mic with a stand. I can't sing.
@@UncleDoug Likewise. Thank you for uploading this video. This is something every guitarist or musician regardless if they use an amp or not should see.
Ive definitely felt a burning cutting sensation on the inner forearm, when I had it resting on the strings, and ive also gotten a shock on my lips on the microphone, not very pleasant.
About 15 years ago, i was playing in my room and had my amp plugged into the wall and the guitar plugged into the amp and not sure how but i out my arm against the strings and got a HUGE shock. My arm went numb for about 5 minutes and then i had string marks for about 2 weeks. Not sure how i electrocuted myself with nothing on that circuit being on other than the amp, but ouch
The strings are grounded to the chassis of the amplfier through the shield of the instrument cable. Apparently, the chassis had a high charge, probably due to the absence of a 3-wire chassis-groundng power cord.
+rock Onmyboi I guess.....unless you grab the microphone stand with your hand, or the sock gets wet from spit. It's probably best to simply resolve the grounding issues and thus prevent any shock hazards.
My first amp was a 1961 Supro 1614N that I inherited from my grandpa(still have it). Anyway, I learned real quick when I was about 13 years old about the shock hazards of 2 prong guitar amps. My room was in the basement and I was playing my guitar in my bare feet on a concrete floor. Let me tell ya......wow! I got hit pretty good. Last time I ever did that! lol
+disarray82 Playing barefoot on cement is indeed a learning experience, Dis. Be glad you survived :) What a great inheritance. The 1614 is a great little amp. I hope you've installed a 3-wire power cord.....or bought some shoes :)
Uncle Doug It was definitely a learning experience.lol Yeah, the 1614 is only 5 watts but it really cranks. As for the 3 prong plug, after my shocking experience my mom took my amp and had someone install one. I still never play without shoes or on concrete floors.
Excellent video. One question though: Is the risk of shock changed when using a piezo pickup (under the saddle) with acoustic guitars plugged into an unsafe amp? If so, how/why?
thanks, I just got an amp that someone gave me of which they broke off the ground lug to use in house with 2 prong sockets, I intend to replace the plug before I feel comfortable using it, the amp buzzes...until I touch the strings which I would guess is a tell tale sign that the amp is un grounded.
Definitely need to get it properly grounded for safety. However that buzzing is normal, you are supposed to be holding the strings to get rid of it. There is electrical noise in the air around you and your body picks it up like an antenna and sends it into the pickups. When you are touching the strings, your body is grounded to the guitar and amp. This helps shunting noise to ground and thus remove buzzing. If you want to stop playing and let go of the strings, turn the volume knob off on the guitar.
I've been a roadie, and many times a guitarist would get a shock from the mic at sound check. It happened so often that they would ask me to touch their guitar, and the mic to be sure they wouldn't get a shock. In all cases, the PA was grounded, and the Amps had a 3 conductor power cord. The floors were dry, (and from other TH-cam vids I've heard that once a 3 conductor power cable is installed , let's say on a 70's Fender amp, supposedly, the "Ground", or "polarity" switch in the back becomes redundant), {the problem was most often fixed by flipping that "redundant" switch}. Then why were we still getting shocks? Can you explain Circulating Ground Currents in a Venue that might have more than one Ground? (e.g., Lighting, PA, Monitors, Stage, House, 3 phase A/C etc...???
Greetings, Jonathan. Once you gather a bunch of electronic equipment, each with its own connection to AC and ground, it's almost inescapable that a potential will exist between some of the metal parts. This potential is evident in the form of shocks of varying severity, as you noted. It would seem that connecting the metal chassis, stands, etc. to earth ground would solve all the problems, but due to the randomness of the circuitry within the gear and the wiring of receptacles, this is not always the case. The one sure way to eliminate this hazard would be to connect all metal-bodied gear with a single earth ground wire, thus eliminating the potential between each item.
I use to have a photo of my SG plugged into a BF bassman with a two prong power cord and a voltmeter across the bridge and tail piece to ground , If I flipped the ground switch on the amp you can see 120vAC applied to the bridge stop ; If I were to touch a microphone whose base was grounded it would complete the circuit .
........and your screen name would become a reality.......Lost. More than a few performers have been fried in this manner. Thank heavens you tested it and (hopefully) solved the problem with a polarized, chassis-grounding power cord......after resolving the dead-short-to-chassis issue (shorted death cap??) within the amp.
Lost, an amp with a leaky "death cap" will usually trip a GFCI outlet. A smart tactic is to plug any newly acquired amp or other electrical/electronic device, power tool, etc into a code-compatible kitchen or bathroom outlet (GFCI outlets are typically mandated) to see if the amp trips the built-in breaker. Probably not a bad idea to use a GFCI equipped power strip for both the onstage equipment AND the house mixer/monitor mixer. It's not a cure-all but it might alert you in advance to a serious shock hazard, or automatically shut off the power so you don't just stand there with seized-up, frozen muscles as you continue to fry....
Here in India we have concrete/cement/tiled floors. In my case, the amp has a three pin supply cord, it's plugged into a "spike guard" that shows you if the connection is grounded, and it was, but I still got shocked. Wearing shoes now to play the guitar, and touching no grounded metal objects with the guitar in my hands.
@Uncle Doug I started playing guitar very recently , Bought new guitar and amp Since its 2020 I had no worries about getting electrocuted Surprisingly the amp i bought (marshall code 25watt) Came with a 2 prong power cord I didn't thought much of it , Didn't know what 3 prongs did So when I start playing nothing initially happened I was sitting on the bed with no carpet or shoe for that fact , in solid ground I got very small but noticeable zap from the guitar after playing it for 10 minutes I bought a 3 prong power cable and started playing on carpet with leather shoes I don't think I have been zapped but I got so paranoid the first time , now I get nervous after playing it for 10 minutes and stop after 10-15 minutes just to not get shocked again
@@UncleDoug To be honest i don't know if the chord works properly or not But why would a new 3 prong cable not work properly? Though I'm kind of curious Is it possible that a 3 prong socket (which the power cord goes into) Does not actually have a ground path? And the 3rd hole is just for the fit and aesthetics? I'm so paranoid (Partly because I Don't have any prior experience to electric guitars or something like this) I'm considering buying a wireless transmitter to calm myself but its extremely expensive Even if it doesn't shock me , im always on the edge ready to jump up if i feel anything You cannot play music like that.. :' l
I am here learning, because yesterday I was playing my guitar into a Fender 1960 amplifier, then someone knocked the door, and when I putted my hand into the door handle Baaaang! !!!! what a Shock!!
Since the doorknob was probably not grounded, the shock may have just been static electricity. Get a voltmeter and measure for voltage potential between your guitar strings (plugged into amp as if playing) and an earth ground (i.e. a cold-water faucet).
Doug, for many years I use EMG active pickups. Per documentation "EMG Pickups are shielded internally and DO NOT require string grounding. This greatly reduces the possibility of reverse polarity shock from microphones and other equipment." Does it mean that I have absolutely no "shock issues" discussed in this video? Thanks.
I am not familiar with the peculiarities of EMG pickups, Pavel, and wonder how a circuit can be completed between the pickups and the amplifier without a two-wire connection. Secondly, I doubt that whatever voodoo is transpiring will eliminate ALL shock issues. My advice is to always follow safe practices when dealing with electronic equipment, regardless of "documentation" :)
And further to this - sticking your hand in amps as Uncle Doug has warned us about but I still got zapped the other day on an amp that I built. I turned in on briefly to check which way the power switch went as I was mounting the amp upside down in a cab and after turning it off I went to turn the switch 180 degrees and shorted across the terminals with my finger and got a nice little buzz. The amp had no speaker mounted and I wonder if this didn't allow the cap's to discharge?
Sorry you got zapped, Freddy. Hopefully your warning will save others from the same unpleasant experience. Generally, the filter caps drain through the (hot) tubes. Since your tubes had no time to heat up, the caps would require more time to discharge. It's always a good idea to manually discharge them with a 100 ohm 10W resistor just to play it safe. You're lucky it was just your hand. If you contact high voltage with both hands, the current will pass through the heart....not a good idea. Hence the rule, one hand in the pocket when working on a live chassis.
Every guitarist should watch this vid. Thanks for this information.
You're welcome, Wm.
I wonder if you ever were a teacher or training instructor, your explanations are very well planed and comprehensive, congrats.
Yes, I was a math and science teacher for 16 years, Javier. Thanks for your very kind comments :)
Uncle Doug
You still have it Mr Doug, I always enjoy a good class or explanation and your videos are some of the best I have seen on you tube. I also enjoy your video on building the finger joined amp, a friend of mine and myself wanna build a custom cab and that is a delux explanation.
Thanks so much, Javier, and best of luck with your cabinet-building project.
@@UncleDoug Completely off the subject of your video, but I can tell you from experience that the best teachers seem to be people that actually were in the industry that they try to teach about. So much more to be learned by experience than from the teacher that just knows the answers to the questions from the book. Four years of math from teachers in high school and the things that stuck with me and made sense were the ones taught by a teacher who was a contractor on the side, he showed how the math actually worked in the real world.
@@mitch3064 Yes, great teachers cover every learning style. Doug is a great teacher.
Thank you Uncle Doug.
Definitely some "shocking" information !
I hope a lot of musicians, especially young ones starting bands see this
very important information that you are providing.
Most mics are isolated from the stand by the plastic mic clips (or holders),
so I always touch the guitar strings to the mic itself, or I just touch the mic with my hand, with the other hand on the guitar strings, checking for any "tingle".
Also make sure your mic stand has all of its rubber feet & are in good condition.
If the feet are worn down to where the metal screws (that attach the feet to the
metal base) are contacting the ground, then the entire mic stand is a path to ground.
I've been zapped while holding my guitar & grabbing a mic stand. It was missing one of it's 3 rubber feet, so the metal base was touching the ground.
Once I had a blue spark from the mic to my front tooth. It almost knocked me out, going right up through the tooth nerve hurt like hell. Not a good place to get shocked.
Since then I check at every gig, especially since there's a different sound company & sound system at each gig.
Greeting, Brian, and thanks for your input on this subject. As a performing musician, your experiences and warnings are especially beneficial to others who face shock hazards with guitars, microphones, and stands. The shock to the front tooth story sent shivers up my spine..... :O
Barefoot on a summer day getting ready to jam in the garage in my high school days, I got the shock of my life from a sketchy amp. That amp speaker later caught fire during a rehearsal!
Thank you SO VERY MUCH. My 8 and 9 year old grandkids got into music this past year. I bought my granddaughter a Martin electric acoustic, mic & stand, and a small Fender practice amp. She wants to be a singer like her GrandMaMah who’s been performing since age 3. By age 5, her GrandMaMah was taught about this. EXTREMELY portant
You're welcome, Elaine. It's never too young to learn about electrical hazards and ways to avoid them.
I think Steve's hair tells the story.
Does anybody remember when Ace Frehley got shocked in Florida at a show and he wrote the song shock me.
I have re-watched this video a few times, and it all finally came together. Thanks for the great informative video Uncle Doug.
You're welcome, JJ. One advantage of YT videos is the ability to repeat portions that require additional study. We're glad it worked for you :)
Great explanation!
You can blow yourself off stage pretty good with bad venue/equipment wiring.
I've toured thru venues with artists, and measured 120V and 220V between a guitar and mic. Sometimes I'd find it myself during setup, other times one of my artists would get it during soundcheck.
I encourage guitar players to invest in a quality wireless systems for their rigs if they're touring. For me, it's a wise investment, simply for the sake of keeping the artist out of the electrical circuit. Typically we keep a few channels of "disposable" wireless around in case we find ourselves doing shows in the rain. Throw the wireless packs in a condom and play the show. Sweaty guitar players are typically harder on gear than the rain.
Thanks, DG. Very interesting......I can definitely see the advantage of wireless gear. We appreciate your input.
Thanks for your kind words, AG. I'm very glad that you are enjoying the videos.
20 years ago, during a jam session in my friends garage, the bass player and I accidentally let our strings touch. He didnt have his fingers on the strings, but I did. I got a big shock and went blind and deaf for about 15 seconds and the reverb unit in my Ampeg head didnt work anymore after that. I assumed one of our amps was screwed up but I never investigated. I used that amp for years after and never had an issue, so I guess it was the old Kustom bass head
Hopefully, our video will help to prevent accidents like this in the future, Steve. Thanks for your input.
Very informative.. your videos are the most understandable and interesting I've been able to find on TH-cam about old tube amps. And by the way your drawing isn't too bad either, I love your sense of humor. Thanks...for passing on your knowledge and years of experience.
I can understand why a musician, faced with an audience expecting him to perform, would resort to drastic measures to keep his malfunctioning amp powered up.....but what a price to pay. This experience would definitely inspire me to have a few spare amps handy if I were ever in Mr. Harvey's shoes.
Learned my lesson tonight and im still a little shaken up from it. playing with headphones plugged into the amp (3 prong) hear some extra static so I go to turn off a small lamp hand gets close to the lamp (2 prong) and bam! muscles tighten up so hard I couldnt even let go of the damn thing until i moved far enough it unplugged and fell out of my hand. probably one of the scariest moment of my life.
Wow.....what a bad experience, PP. I had a similar one many years ago and actually experienced heart palpitations. We hope you resolve the wiring issue and never have a repeat of this scary event.
I had this just today for the first time! super scary. Should've seen this video beforehand!
I'm glad you survived it, BT......240VAC will really get your attention. Although your experience was not amp related, I feel compelled to mention that when working on a live chassis, it's a good idea to keep one hand in your pocket....that way you can never accidentally complete a circuit from arm to arm (through your chest and heart) that might be fatal.
Someone else that works on amps told me that too. I have a Fender Champ 600 to fault find so will ensure I abide by that method. I'll probably also wear a nitrile glove on the other hand 👆. The amp gave up, it used to run rather hot for its mere 5W (output). Previous owner had someone install a modification kit consisting of an improved rectifier, DC heater supply and standby switch. I suspect they failed to follow the final part of the modification instructions (that I have obtained) that should check and adjust (resistors) to set the correct voltage to the tubes. So carefully checking that could be my starting point.
@@SaxJockey That sounds like a good place to start, SJ. Good luck with your project.
Thank you so much! I got shocked recently at home while playing guitar and this video helps my on my way to understand how all of this works and how to remedy the situation. Nice drawing by the way :)
You're welcome, Rurzan. I'm glad the video (and drawing :)) were informative.
Have you seen the video by "Woodeso's guitar mods?" This guy has his left hand on his strings than grabs an ungrounded metal lamp post and gets zapped. He broke loose by falling and knocking it loose from his hand. This goof ball doesn't even know why it happened and thought it was funny so he still has the video available to watch...you should probably give him a heads up and tell him about the death of Keith Relf from the yardbirds.
+Steven Spencer This guy sounds like a good candidate for the Darwin Awards, Steven. I'll try to find the video.
Late, but let's hope this is a still useful reply:
th-cam.com/video/trY4lNdz-ks/w-d-xo.html
@@UncleDoug here is the video, electric shock occurs shortly after 3 minutes and 30 seconds: th-cam.com/video/trY4lNdz-ks/w-d-xo.html
Thanks for this video, Doug. My personal philosophy is -- originality be damned, any piece of vintage equipment I have gets a proper grounded plug. I learned my lesson many years ago when I had the "ground" switch flipped the wrong way and high-fived my bandmate after a particularly awesome rendition of Into The Void.
Jason Thorpe I understand, Jason, and agree that any equipment that will be used commercially definitely should have a grounded, three-wire cord. On pristine, vintage equipment, receiving limited use at home and in controlled conditions, I tend to favor originality, as long as the precautions I have described are followed.
Been there. For me, the show came to a stop until things were sorted out. In dive bars where things were too weird, we either did a straight acoustic show or we cancelled.
.....and due to concern for your own well-being, you are still with us, Michael, and able to make comments on our videos. We're glad :)
Hello! This video has been really helpful!
I wanted to tell you about the problem that i've been having with my equipment. Maybe you could help me find out what seems to be the malfunction..
Recently i bought a brand new electric guitar and an used 10w amp (this because of budget issues haha) and i've been experiencing electric shocks whenever I touch the power switch of the amp. This amplifier has the three plugs.
What i've noticed in these couple of days since I bought all of this equipment, is that I get the shock when I touch the amp (while is connected to an extension where I also connect my PC, the monitor and desk lamp) at the same time that i'm grabbing my guitar..
I plugged the amp directly to a socket and did'nt receive any shock that way.. but in reality i'm a little afraid to confirm it again..
What are your thoughts? I'd really appreciate if you could help because this has been kind of a bummer
Does the extension cord have 3 wires.....or two? Most have only two and do not provide any grounding capability. If no shocks occur when you plug the amp directly into the wall, then this is the ONLY way it should be plugged. I have no idea what type of amp this is, but it seems to have internal grounding issues that may need to be addressed.
@@UncleDoug the extension i've been using has three wires and this has been happening only with the Amp. I have also connected my pc and monitor to this extension and never gave me any problem.
And the Amp I bought is a Vox pathfinder 10, wich i got from a local music store in very good conditions and used!
@@gabo_caruso If there is no shock when the amp is plugged into the wall, but there is a shock when you use an extension cord, then it would seem that the cord, regardless of how many wires it seems to have, must be the cause. The PC has an insulated body and would not be a reliable comparison.
@@UncleDoug Today I tried both ways: Amp connected to the extension and then connected to the wall. And in both ways I felt current coming out of the amp's chassis (doesn't hurt or anything), specially when I put my finger over the power switch. Also happens with or without the guitar plugged to the amp..
There must be something wrong inside the amp i guess.. But the weirdest thing is that in the music shop, this didn't happened at all.. It's happening where I live.
Anyways, your responses have been very helpful! I really appreciate it!
@@gabo_caruso Your electrical receptacles may not be wired properly, Gabe. You can buy a cheap device at Home Depot and test them.
Thank you this was very helpful and important safety information! I could see how that would be an issue at outdoor concerts.
You're welcome, AW. Glad you enjoyed it :)
Hi uncle Doug about 35 years ago I experienced this. thank you for putting this out to musicians and techs,I was in our studio with our singer the whole rm was covered with carpet summer day hot as hell sweating my guitar strings welded to the mic stand. my lips touch my mic to sing and boom blue ⚡️ sparks I tried to scream nothing came out I was picked up an thrown against a old wooden chair that broke to pieces my singer told me what happened when I came to the polarity on his PA and my amp had changed. I didn't feel so good and didn't play guitar for a week . I guess I'm Lucky to be alive ...thank you for your top notch videos I love em...
You're welcome, LL. We're glad you survived this ordeal and took the time to warn others about the shock hazards associated with polarity differences in equipment.
Thank you and Rusty
Musician Safety: Touch your plugged in guitar (strings) to the Mic stand & see if it arcs.
If it does, don't touch it. Call a Licensed electrician.
Good advice, C&C.
Yes, Uncle Doug. I had the mic thing happen. Had my Les Paul Gold Top plugged into my 100 watt Ampeg V4. I boldly stepped up to the mic to sing, when out of nowhere, a purple caterpillar appeared and jumped from the mic to my upper lip. It bit me and vanished just as suddenly. I started singing the song a cadence later, and did so from six inches away. Stuff like this used to happen all the time, and we usually held our plugged in guitar in one hand and smacked at the mic stand and each other to check for a current differential. It was the poor kid's volt meter.
By the way, heard Rusty's guitar solo on one of your other videos. It was masterful.
Addy Adderson Greetings, Addy. Thanks for sharing your "shocking" experience with mixed polarity in musical equipment. The "poor kid's volt meter" analogy was great :) Rusty sends his regards and appreciation for your kind appraisal of his musical skills :) ^. .^
Thanks again for watching, Ron. Good luck with your own project(s).
Aaaand now I'm shopping for new mic stands with rubber feet...Thanks, great job, Uncle Doug!
It won't help if the metal parts of the microphone or stand are of a different AC polarity than the strings on your guitar, AJ.
I'll never forget at a practice in an old warehouse in jacksonvile florida got an arc from the mic and the lights dimmed, ouch! I hate when that happens
I'm surprised you survived, David. To dim the lights, the current draw must have been substantial, and it only takes 100mA or so to kill human.
Thanks, Frank, I value your opinion and your approval means a lot.
I plugged my old guitar into a gen 1 Boss Katana amp and I got a HUGE shock... By how good it sounds!
That's the type of shock we can live with, William :)
Uncle Doug says: "All you do is this, take the guitar, and touch the strings to the microphone stand, and watch what happens. If theres a big blue arc (it looks like an arc welder just fired up), do not under any circumstances come up here and start singing into this microphone." - Thats some good advice right there! Thank You, great video!
Thanks so much, Matt.....glad you liked it. I got a little hyperbolic, but it's a reliable, simple test. Even tiny sparks indicate that a serious problem exists and has to be corrected. Thanks for watching and posting your comment :)
An excellent suggestion......GFI's are a great safety measure. Thanks, Frank.
SO important, Uncle Doug! Thanks for spreading the word!
It's our pleasure to do so, Thomas.
Uncle Doug- splendid presentation! I'm grabbing my multimeter right now. Thanks, man.
Thanks, AG. I hope the reading is 0V :)
Now I know why my fingers tickle when I play barefoot in the garage! Thank you for the valuable information, sir.
You're welcome, Jesse. It can be quite serious.....so be careful.
Yea, can feel the voltage in my knuckles.
And there you thought you were getting tingling hot😉
Anything you say is 100% correct and relevant; however I prefer to talk intensity and resistance, which are easier to understand for most people:
a) the danger is current intensity for the human body: 30 mA, across the chest, cause muscles tetanization (heart and lungs blocking, inducing terminal syncopes and rapid brain melting)
b) the human body resistance varies between 100 ohms and 1000 ohms (depending of your health condition , weariness and stomach content)
* most deadly electric shocks occur between 11-12 am and 17-18 pm when workers are hungry (official accident stats in french data base)
So a tension of 0.03x1000 = 30 V is potentially lethal (maximum allowed in High schools and College physics labs, in France)
So ALWAYS use an amp with a 3 wire cord, grounding the chassis and the metal parts on your guitar... Please update your vintage tube amps (discard the cloth woven wires and ignore the self proclaimed "tube gurus" opinions: it might save your life, at ultra low cost...)
In continental Europe, we have 220 to 240 V power outlets : it's not forgiving!
240 V /1000 ohms = 240 mA = a one way lane to BBQ heaven
240 V / 100 ohms = 2.4 A = the frying pan
great video as always... BS free speech, coming from someone who knows what he's talkin about
Thanks for your detailed analysis, Serge. Your advice is excellent and definitely worth knowing by all.
I wouldn't think that the field coil of the speaker would be a hazard, but if one shocked you, then maybe so in the case of this unusual amplifier. You can test it with a voltmeter like I do in the Death Capacitor video. Connect one lead of the voltmeter to a good ground and then touch the other lead to metal parts of your amp when it is plugged in and turned on. If there is any shock hazard, the meter will give a reading of the amount of voltage present in the chassis and speaker.
this is hella interesting and the only good video i have found on this topic.thanks for making it
You're quite welcome. Thanks for posting such a nice comment :)
Hello again! This is a good video for many players to watch...I try to explain this to many guitarists who's amps I repair, but they look at me funny :) I tend to explain it tech terms and sometimes I don't realize it and think I'm talking to another tech...But this video explains it in simple comprehensive terms for the non-tech person...another great video! :)
You may have saved my life by making this video...I have zapped my lips on mics many times...and shocked myself on my amp's chassis several times in the past...my amp is circa 80's point to point -100w with 3 prongs but I suspect I have a grounding issue...I am going to check things out with a volt meter as you suggest. Incidentally, I once saw a video of Hendrix rubbing his guitar against his mic stand...perhaps more as a precautionary, rather than artistic measure.
Bob Flint If the video prevents you from receiving a serious shock, Bob, then it truly served its purpose. You really need to investigate the cause of the shocks you have been receiving. Bear in mind that the fault may well be in equipment other than your own. If your amp and guitar strings are properly grounded, then you become grounded when you touch them, and electricity from any improperly wired equipment you come in contact with will try to pass through you to that ground. Jimi was checking to see if his (grounded) strings were attracting an electrical spark from the mic stand before he came in contact with it. It's a standard test, as mentioned in the video, and sort of a last resort. A little portable voltmeter can do a better job of assessing any potential between pieces of equipment and can save your life. Best of luck.
With that being said, I think I've discovered something that I thought was just a fashion statement or that looked cool. Especially in the sixties and seventies when amps and equipment didn't probably have three prong electrical cords, bands would have all these beautiful rugs on the stage that look very cool and even today, well maybe this helped them the musicians from getting electrical shock all the while looking so cool when the Greatful Dead played.
Rugs and rubber mats would be a good precaution, Ron, particularly if the stage was metal. If the performance was outside and it rained, however, all bets are off :)
Yep that explains it! I was bare footed every time on the polished concrete floor of my garage! Got shocks from the strings after playing my Strat appx 10 mins. I was using a Vox mini practice amp with a 9V DC adaptor. Thanks for the explanation.
Rusty and I are glad to hear that the video was helpful, L1. Thanks for watching and commenting :)
lanthaniated1, Hmm, now how could this happen? the only way I can see that you would get shocks from a 9 volt wall wart adapter is if it was seriously defective or seriously designed him properly. Perhaps it uses a transformerless "switching" power supply? and/ or was additionally defective? a different wall wart adapter might cure this problem. here's a hint, if the 9 volt adapter seems very lightweight like it's all plastic almost, it's probably a switching Supply. Anything with an actual Transformer is going to be a bit heavier. The switching supply will have some inductor coils in it but usually it's not very big on the copper wire content nor does it have the steel core necessary for a Transformer.
Welcome aboard, Steve !! :)
I'm a little confused by the question, AR, but the word "potential" means a difference in electrical charge between two objects or locations. If a connection is made between them, then a current will flow from the one with too many electrons to the one with too few. If a potential exists between an amp chassis and ground, and if you touch both, an electric current will flow through you from the chassis to ground.
🔥 this is a very very overlooked subject and I'll never forget the shock I got off my 1970 200 watt Marshall major because of that pin plug for the ohm adjustment bounced out was not a good scenario
Thanks, Charles. Glad you survived :)
@@UncleDoug you are the best Uncle Doug🤞💜
Very good information! Thanks for all of the videos you've posted.
zarbog8 61 You're welcome, Z. Thanks for watching :)
Thanks for the straightforward advice. Very informative.
You're welcome, Milo.....glad it was helpful.
Fantastic video. Thanks so much for help keeping us all safe.
You're welcome, Gordon.
Great video. Had a band mate get a shock off a mic stand once, and this is in the UK where everything should be ground wired. He played on against my advice, but thankfully survived!
It happens a lot, Alex, and hopefully the video explains why and how to avoid these shocking experiences.
+Giath Majstorovic I've never had any venue ask for proof that gear was PAT tested, and we've played a lot including some medium sized festivals etc. In any case this was the venue's gear so wouldn't have helped!
makes perfect sense - will do the test before the amp is serviced and then again, to see if there has a hazard from the field coil or any other parts and then after as well. i should be sure then.
thank you for the great videos you've been making - they way. it is a great library of historical amps and also very educating.
with tis words i'll say "greetings ;)"
Perfectly clear,thanks!
This was such an important and well done video. Thank you. You couldve saved lives.
You're welcome, GT. I sure hope so :)
First off all , Thank you for sharing your knowledge and taking up your time for doing all of the Topics on Tube Amplifiers . We spend all the Money thousands of Dollars /Euros or what ever, to buy the fanciest Gear , Amps , but most
of us we don't have the Money to buy a Power Source for our Amps to provide us and our Amps with the needed and save Electricity where ever we go, this Power source must have the capability to shut off the Power as soon you have a ground loop or other electric malfunctions, or in the case some of our equipment catches Water , like a residual current circuit Breaker I hope this is the right Term for this. Here in Norway are existing very old Houses where the 240 V come in 2 wires 120 Volts each , a I forget how they go to ground if it existed . This should never occur this times but you never know . And today the Ground Lift switch and the Death cap are forbidden in Europe , because those devices led to many injuries or deaths. One thing , I don't do Patreon so if you let me know how I can support your Chanel in another way , please use my e-mail for this .
Thanks so much for all your nice and interesting comments, PB. I include contribution information in every video description.
Doug - always great work. You are very appreciated.
Just a couple of thoughts: The microphone is usually attached to the stand with a plastic or hard rubber clip. This would pretty much isolate the mic chassis ground from the stand. Also, many mic stands themselves have rubber feet to keep them off ground. In that case, touching the guitar strings to the mic stand won't do anything, other than charge the stand.
Thanks, Paul. Rubber feet or not, if the microphone and/or stand have/has a polarity opposite that of the guitar strings, a potential will exist.....as will a shock hazard. The potential between microphone and ground is immaterial. All that matters is whether, due to improper wiring and mixed polarity, a potential exists between any two pieces of equipment. This can be prevented by the proper installation of polarized, 3-wire, chassis-grounding power cords.
Thanks, F86. I just watched a video of his and couldn't resist. I probably should have included a cigarette on his lip too, just to make it more realistic, but the smoke might have made it look like he was being electrocuted ;)
Hey Rusty, hey Doug. There is one thing that imho is very important to mention, when it comes to discussing the danger of electric shocks on guitar amps... I´m talking about the condition of your mains plug... I´ve seen many in very bad shape (always the european style, of course) - sometimes the plugs were not even properly fixed to the outer shell of the cable... If the ground-wire gets ripped off inside the plug and touches the pin that carries the 120V (in our case: 230V) it becomes very dangerous...!!! If you´re playing your guitar in this moment, there will be hardly any chance to get your fingers off the strings anymore, as your muscles will be convulsing... Dogs are more safe, as they cannot put their paws around a guitar neck and they do have some additional fur-insulation...!
A good point, Sal. Plugs, especially on amps carried to and from performances, can get trampled and damaged, so their integrity must be checked regularly. Rusty says that he has been shocked several times during gigs, but a couple shots of bourbon (both before and after the shock) seemed to make his paws feel a whole lot better :)
This kinda explains how i got shocked. About a year ago i bought a sears catalog amp from the 60s and i had it cranked. Went to touch another amp of mine that was on and immediately i got shocked like hell. Even had a giant red streak going from my arm to my chest
You're lucky you survived, G&G. The electrical path passed near or through your heart......the worst possible scenario. Please heed the warnings in the video and stay safe.
@UncleDoug thanks uncle Doug. I learned thankfully, this video gave me even more information. Now that amp is more of a decorative piece lol
You're welcome, G&G. Merry Christmas :)@@guitarandgames1386
I got a good shock once playing in a garage. I thought I was just rockin' real hard!
The endorphins can give you a buzz, Andy, but 120VAC can really sizzle the old scrote :)
thank you
We Miss you Uncle Doug!!!! & Jack & Rusty. Please Come back ….anyhow God Bless you & yours.
Thanks so much W4. We really do intend to post some more videos. Sorry for the lengthy delay.
An outlet checker is cheap, and provides some clue if the condo or club was wired right. Once, I was resusing an industrial outlet strip, when I noticed that Hot was wired on the larger blade of the plug. I opened it, it and rewired it.
~
Perhaps for amps where the original 2-prong unpolarized cord remains in play, perhaps a sticker or a paint spot could mark which plug blade is neutral.
~
I used to disconnect the bridge wire from my guitars. I suspect that they had hoped that the strings might shield the pickups, and having the strings grounded might have helped. (Still the plug, jack, and pickups might be hot, but anyway....)
Well, perhaps a compromise could be made. I got the idea from anti-static wrist straps. They have a 1 meg-ohm resistor in them to limit the current. Perhaps a resistor such as a 1k-100k ohm could be wired in series with the bridge wire, then the strings can still be part of the shielding solution, but at least the current is limited, and the voltage is much lower.
Thanks for the videos.
You're welcome, Brenda. Thanks for the helpful comments.
The main concern, from a shock standpoint, has to do with the AC part of the circuit, since "ground" for that circuit is just about everywhere.....pipes, cement floors, door frames, etc. The DC circuit is restricted to the chassis and can kill you if you reach into the chassis and touch highly charged areas with both hands....but who does this, unless they are actually working on the amp? AC can get to the chassis through any short in the primary circuit between.........
You're welcome, Philo. I hope it all made good sense.
You Sir are a great instructor. I just put my DMM across the chassis of my beloved two-prong plugged Kalamazoo Model One, got almost 4v, flipped the plug over and got 113v. I now know how to deal with it thanks! I owe you dinner at L&J
Thanks, Jeff. I'm glad the video was helpful, but please be careful with any amp that has potential within the chassis. Have you considered installing a polarized, 3-wire, chassis-grounding power cord ??
Yes thanks I'm on it but for that I'm also going to buy you breakfast at said restaurant
Your choice of restaurant is intriguing. It wouldn't happen to be on East Missouri Ave. would it ?
Si Senyour
Then you must be a local lad. Any chance of changing it to the Riviera on Doniphan ???
Yep, I learned the hard way in 1965. Amps should have GFI circuits
Maybe the shock was due to excess perspiration ? ;)
Good video Doug ! It'samazing how an old amp can shock you or not just by flipping that two prong plug. I'm a big fan of grounded plug.
Thanks, Bobby. I agree with you re the three-wire grounded cord, especially if you are going to set up your equipment with other equipment of unknown polarity and grounding. As my old granny used to say, "It's always better to be safe than sorry."
Hi Doug. Love your channel...just a thought. all modern microphone clips are plastic so people won't get a boot off the stand but through the mic grille. so a better safety check would be to touch the strings to the mic before. as you say tonguing the microphone! Cheers from New Zealand
Greetings, Mike. Thanks for the helpful tip.
And by the way, my other amps work normally from the same outlet, and the amp is solid state. It also pops loudly when turned on, and it wasn't on when I got the shock. It also has a circuit breaker on the back of it, and I believe a fan inside of it, and is supposively 880 watts solid state (coliseum 880) thanks for the video
You're welcome. Be careful with that monster.
Really nice explanation!! Thank you so much. :)
You're welcome, JJ :)
I've gotten the mic shock more times than i can remember.
The worst was at this small club while using someone else's amp. It was old and rugged looking, plus the power situation was complete mystery. I just showed up in a hurry with my guitar and plugged in. The shock i received when i kissed that mic was so bad, it rendered me completely unable to process any thought for several seconds. I just stood there looking like some ancillary character from rick and morty. That stuff is no joke under certain circumstances, man. If it was any worse, i could've easily passed out.
Thank for sharing this story with us, MG. It should help make people more aware of the risk they take when using improperly grounded equipment.
I've been feeling the tingling sensation on my fingers everytime we jam and i once got shocked real bad(it scared the shit outta me and really painful) the time i accidentally took my foot off my footwear and stepped on the concrete, i had no explanation why,its always been a mystery but not anymore, this video explains it very well, it makes sense now, thanks,😄🙏🙏
Please be safe, LB. It really can kill you. Be sure you are insulated from concrete and that your equipment is properly grounded with 3-wire power cords.
@@UncleDoug 🙏 i will, thanks again
Well that clears things up, really wish manufacturers would put stuff like this in users manuals for people that don't know that if you ground the microphone cabinet and your guitar amp isn't grounded you get shocked and there is a possibility you could die. From now on (as far as I know) I'm not gonna "reduce the hum" on my Alto 12 inch speaker by grounding it because it could be fatal. I live in Poland so the plugs don't have 3 prongs and therefore are not grounded, meaning my Vox AC30C2 isn't grounded, so that's that
Also, got to get a windscreen for my mic to further reduce the risk
Are the sockets polarized, Hubert ? One tall slot and one short slot. In the U.S., the shorter slot is the "hot" lead. If they are, then it would be helpful if all your gear had polarized plugs.
11:35 FYI The microphone may be insulated from the stand by the plastic clip. You must touch the strings to the microphone itself while holding only the wood on your guitar.
Thanks for this added detail, Tim.
@@UncleDoug Just sharing a lesson that I learned the painful way. Thanks for your nice videos.
@@Timbretwo We appreciate it, Tim.
I had a similar experience last summer playing a gig on the beach. Since it was warm, I took off my shoes and immediately started getting an alarming tingling feeling from my strings when standing on the sand. I was also having all sorts of buzzing problems with my amps and pedals and couldn't figure out what was going on. After the gig (successful despite the problems), I talked to my friend who is an amateur tube amp builder, and he explained grounding issues to me.
Now all my gear is properly grounded with three-prong cables, and I always take good care of it. I discovered early on that missing ground could result in buzz, so I was quite puzzled. Then I remembered that the venue owner connected our stage with a cheap Chinese 30m extension cord which was buried under the sand... then it clicked 🙂
Moral of the story: Your wall power source might not be grounded, so no matter what you do, safety measures still apply.
Thanks for the very informative input, G. You're right that all wall receptacles should be tested for proper wiring. After living in my house for almost 30 years, I discovered that a receptacle in my amp room was wired backwards (black to white).
@@UncleDoug Ah, that's a bummer! Same here in Italy - I talked to another musician and they said grounding issues are pretty common at small venues. Apparently, the only workaround they knew of was sticking a metal pole in the ground and connecting it to some metal part of the equipment to create a makeshift ground.
I'm wondering if that's safe and if there are better ways to test the receptacles on-site?
@@galacticx738 Receptacle testers are readily available at Home Supply stores or on Ebay. The metal pole in the ground is a classic way to provide earth ground. Be sure the ground is damp around the pole.
@@UncleDoug Thanks for the response, will definitely give one of those socket testers testers a try!
@@galacticx738 They are cheap and effective, G. Good luck.
I like making radios and amplifiers. Always with a 'cold' chassis of course.
Old radio sets can be pretty dubious where safety is concerned. The old UK standards allowed a 2 pin plug which could insert the wrong way, like the American plug.
I have had cheap radios without isolated chassis & only a single-pole mains switch on the 'cold' wire. Pretty horrific, even though standards were different back in the day.
The stuff I make is waaay better.
NJPurling I guess people were tougher back in the "good old days"......and less likely to sue for pain and suffering " :)
I have managed to electrocute myself. One time only.
I landed on my bed so damn hard the frame cracked. It is plated with some aluminum sheet to this day.
The Grim Reaper ain't getting another chance, no siree.
I make sure the damn plug is out of the socket.
An old radio guy told me a good peice of advice: "Keep one hand in your pocket"
Obviously if the charge flowed up one arm and the other was the ground the electricity is going to mess up the function of your heart.
Game Over!
Yes, indeed. I am definitely an advocate of the "one hand in the pocket" school of electrical safety :).
I have survived a dose of 230V & lived to tell the tale. Broke my friggin bed frame tho when I landed. I had to plate it with aluminum I was keeping to make a chassis.
Never again! Not only do I pull the plug I make sure it is plainly visible to me.
I hear you, NJ. I've heard that 230VAC can deliver a fearsome jolt. Thank heavens it didn't pass through your chest.
It was a helpful video.Last month I was playing wid my guitar I felt a slight shock at the 3 fret.I thought it was crackling of my finger bone but later on it was occuring again and again.From that day onwards I make sure that I wear rubber shoes while playing guitar
Harshad Shriyan Harshad, if you're getting shocked by your guitar strings, you need to check the ground wire on your amp chassis and ensure that your electrical outlets are properly wired and provide a good, solid ground. Ignoring this problem might lead to worse shocks and even bodily harm.
I checked the grounding of both the guitar and amp and the all the electricals it was all fine.
Can processors eliminate this shock issue?
I am not sure about the effect of a processor, Harshad. I guess you'll have to try one out and see if it helps. Good luck.
Thanks the information helped me alot
Regarding what you said at 2:38: If I understand this correctly, the electrons can flow into your body through the cable shielding, but not through the cable itself. Is this because of the high impedance of the cable (typically reater than 10,000 ohms) delivering the signal to the pickups? If so, what would happen if you touched the pickups, or just the guitar cable? For example: I have never heard of anyone getting shocked from touching a tip of a guitar cable with the other end plugged into the amp. Thank you for the great video!
Matt, the reason the shielding is implicated (and not the signal wire) is that it is connected to the amp chassis (the source of the shock hazard) and the parts of the guitar that you come in contact with. The signal wire is not. If it were, and this is something that many people have encountered with incorrectly wired jacks, there would be a loud hum from the speaker because the metal parts incorrectly connected to the signal wire would act as an antenna to extraneous noise. The loud hum would force you to correct the incorrect wiring. With correctly wired jacks, the tip of a guitar cable cannot carry any harmful voltage or current.....it connects to the grid of the first pre-amp tube where no such voltage or current exist.
I just recently found your channel, that's another great video uncle Doug! you also have great drawing skills, who wants fancy screen graphics when you can produce this kind of artwork !
Wow, thanks, Benj. Actually Rusty draws all the diagrams......I just wave the pointer around and try to sound authoritative :) :) :)
Uncle Doug
Amputee
Apologies in advance for the length and details of the following post, but here are some "shocking" scenarios I have encountered in person. 1) I have a Dan Electro amp with a top-mounted preamp that includes a couple of tubes as well as the volume and tone controls, with the main amplifier chassis on the bottom of the amp facing the rear and incorporating a pair of 6 L 6s and the 5 y 3 rectifier and a driver tube. There is a wiring harness of four or five wires as I recall going from the amp chassis up to the top mounted preamp, and there's also a shielded RCA cable with bare metal shield, uninsulated, coming down to the amplifier from the preamp to carry the audio signal. As I was working on it and trying to track down some intermittent noises, I had unplugged the RCA cable joining the preamp and an amp to see if the noise problems still existed with the preamp audio drive disconnected. At some point I went to plug that RCA cable back into the amplifier chassis while it was turned on, with my right hand leaning or braced against the amp chassis , and my left hand grasping the unshielded RCA jack and cable. Apparently, the preamp had no power supply ground, much less audio ground, included in the wiring harness, and instead the electrical ground was being made by that RCA cable being plugged into the amp. As I worked on the amplifier I unwittingly became the ground path between the top mounted preamp in the bottom mounted amplifier, and because the preamp had high voltage running to it to feed the preamp tubes*, and I had already added a grounded cord to the amplifier chassis, I got one heck of a shock. Needless to say, I added a separate top to bottom ground wire to permanently connect the two pieces electrically, and I disconnected the RCA shield on one end because it was no longer needed as a ground, and also to prevent ground loops.
Anybody who has a vintage amp with a 2 chassis set-up, not just an actual top mounted preamp incorporating tubes and circuitry, but perhaps just a passive input jack panel with volume and tone on it, should really check the grounding scheme for safety, especially if there is a tube or tubes in the top half of the system, and also to see if the shielding of the audio cables is being used as the main and only ground in between the top input jack panel and the amplifier at the bottom of the cabinet. I worked on a very cool old Masco amp a while ago, I think it was a 120n or similar, and although the top-mounted input panel did not have any tubes in it, it hummed really badly until I ran a ground wire from top to bottom and disconnected the shields of the audio cables at the top panel by the volume and tone control.
Perhaps the least safe design of a consumer electronic product that I ever saw was an old compact but heavy Califone record player, with a completely all- metal silver grey chassis and a built-in speaker, that was probably meant for school usage. This thing was a transformerless amplifier that had a voltage doubler, or was it a tripler? that was fed directly off of the AC line cord !!!!!! It actually had an RCA black plate 6L 6gc run single-ended, and a fairly beefy output Transformer, and a single 12 ax7, but it didn't have a power transformer! I wonder how many children and teachers got a nasty surprise from one of those!? I have seen two of them, they were cool to steal the output transformers and tubes out of, but no way would I want anybody to use one nowadays! Not to mention that the tonearm probably weighed three or four pounds. you could probably plow a cornfield with the stylus pressure from that thing!
*That particular Danelectro (can't remember the model number, I'll have to look it up) zapped me even harder then you might expect because it has an unusual design, whereby the series-wired filaments of two 12 ax7s are fed approximately 24 volts DC directly off the combined cathodes of the 6 L 6 output tubes, and the resistance of those (2) 12 x 7 filaments or heaters actually forms or comprises the "cathode resistor"! This is a variant of an old hifi trick that lowers noise because you would normally be "wasting" 20 or 30 volts across the cathode resistor for the output tubes, and sometimes you'll see an amplifier that has the cathode resistor and still uses that 20 something volts found at the output tube cathodes , above the cathode resistor to ground, to drive the heaters of a couple of with some clean DC voltage, but in this particular case they eliminated the cathode resistor entirely !!!! Anyway, the two 12 ax7 heaters are connected to the chassis of the top preamp on one end , but when I was fiddling with the amp those 12AX7 heaters temporarily didn't have a ground connection, which means that the output tubes didn't have a cathode to ground connection either, so the B+ voltage at the 6l6 plates was also present at the 6 L6 cathodes, and looking for a path to ground, which it found by passing through the cold low-resistance 12 ax7 heaters and through the RCA cable shield and through my arms and chest to the chassis. The upshot is that whatever the main B+ to the output tubes was, some 430 olts or so as I recall, I got virtually all of it !
Wow....a very informative and somewhat scary commentary, GU. Thanks for helping to impress viewers with the importance of electronic safety procedures.
You might think twice about getting that vintage gear off eBay or Reverb. I know for a fact older neighborhoods in the Northeast ( where I live) have some houses with two prong outlets with fuse boxes instead of breakers. Some people replace the two prong outlets with three and don’t ground them. I carry a wire tester that I use before I plug in my amp.
That's a good idea, Dave. Thanks for sharing.
I have found that, if the chassis is HOT you can feel hum on the metal parts with the back of my hand. if there is hum then changing the direction of the two prong plug usually puts the chassis closer to ground..
Greetings, Dan. I can think of no reason why a properly wired chassis would be "hot". There are no direct connections between the primary circuit and the chassis, other than perhaps a leaky "Death Capacitor", which is rather uncommon. If the chassis is indeed energized, the source of the leakage should be detected and eliminated. Then, installing a 3-wire chassis-grounding power cord would eliminate the possibility of any further issues.
Important! (Oops) Thanks again for illustrations, also! Love it.
You're welcome, Elaine :)
I have this same problem with a vintage open reel tape deck. I get a small shock when touching the chassis of the deck and a metal framed shelf. I plan to open up the deck and find the bad capacitor, and replace it. Before I use it anymore.
Greetings, MM. Your shocking problem may not be due to a capacitor, and it may be a health risk. Your best bet is to install a 3-wire power cord in this tape deck and be sure the green (ground) wire is securely attached to the chassis. Don't take chances with this.....it really needs to be done.
Uncle Doug I sent you a PM describing my problem in more detail. Including voltage measurements in several different situations. The shock is annoying but not lethal. I haven't tried grounding the chassis yet. Afraid it might damage my deck in this condition. Please read my PM and advise. Thank You.
I'm glad I play the electric guitar as a hobby at home with a USB Audio Interface to my computer using Guitar Rig 5. I never got shocked once, I always wear rubber sole shoes on the carpet in my room when I play. My hands sweat sometimes but that's never been an issue either. Also no, I don't have a mic with a stand. I can't sing.
Thanks for sharing, Spirit. Stay safe :)
@@UncleDoug Likewise. Thank you for uploading this video. This is something every guitarist or musician regardless if they use an amp or not should see.
@@TBM_Spirit It was our pleasure to do so, Spirit. Thanks :)
Ive definitely felt a burning cutting sensation on the inner forearm, when I had it resting on the strings, and ive also gotten a shock on my lips on the microphone, not very pleasant.
Thanks for sharing, IM.
Thanks for the PSA!
You're welcome, Riloh. We care about our viewers :)
About 15 years ago, i was playing in my room and had my amp plugged into the wall and the guitar plugged into the amp and not sure how but i out my arm against the strings and got a HUGE shock. My arm went numb for about 5 minutes and then i had string marks for about 2 weeks. Not sure how i electrocuted myself with nothing on that circuit being on other than the amp, but ouch
The strings are grounded to the chassis of the amplfier through the shield of the instrument cable. Apparently, the chassis had a high charge, probably due to the absence of a 3-wire chassis-groundng power cord.
Put a windscreen or sock over the mic. Solves the different ground potential issue as well.
+rock Onmyboi I guess.....unless you grab the microphone stand with your hand, or the sock gets wet from spit. It's probably best to simply resolve the grounding issues and thus prevent any shock hazards.
My first amp was a 1961 Supro 1614N that I inherited from my grandpa(still have it). Anyway, I learned real quick when I was about 13 years old about the shock hazards of 2 prong guitar amps. My room was in the basement and I was playing my guitar in my bare feet on a concrete floor. Let me tell ya......wow! I got hit pretty good. Last time I ever did that! lol
+disarray82 Playing barefoot on cement is indeed a learning experience, Dis. Be glad you survived :) What a great inheritance. The 1614 is a great little amp. I hope you've installed a 3-wire power cord.....or bought some shoes :)
Uncle Doug It was definitely a learning experience.lol
Yeah, the 1614 is only 5 watts but it really cranks. As for the 3 prong plug, after my shocking experience my mom took my amp and had someone install one. I still never play without shoes or on concrete floors.
You're mom had the right idea, Dis. Glad to hear that you still have the amp and are doing well :)
Excellent video. One question though: Is the risk of shock changed when using a piezo pickup (under the saddle) with acoustic guitars plugged into an unsafe amp? If so, how/why?
No.....the type of pickup doesn't matter. It's the shield in the guitar cord that connects the metal guitar parts directly to the amp chassis.
thanks, I just got an amp that someone gave me of which they broke off the ground lug to use in house with 2 prong sockets, I intend to replace the plug before I feel comfortable using it, the amp buzzes...until I touch the strings which I would guess is a tell tale sign that the amp is un grounded.
You could be right, JD. Be careful with it until you get the chassis grounded again.
Definitely need to get it properly grounded for safety. However that buzzing is normal, you are supposed to be holding the strings to get rid of it. There is electrical noise in the air around you and your body picks it up like an antenna and sends it into the pickups. When you are touching the strings, your body is grounded to the guitar and amp. This helps shunting noise to ground and thus remove buzzing. If you want to stop playing and let go of the strings, turn the volume knob off on the guitar.
I've been a roadie, and many times a guitarist would get a shock from the mic at sound check. It happened so often that they would ask me to touch their guitar, and the mic to be sure they wouldn't get a shock. In all cases, the PA was grounded, and the Amps had a 3 conductor power cord. The floors were dry, (and from other TH-cam vids I've heard that once a 3 conductor power cable is installed , let's say on a 70's Fender amp, supposedly, the "Ground", or "polarity" switch in the back becomes redundant), {the problem was most often fixed by flipping that "redundant" switch}. Then why were we still getting shocks? Can you explain Circulating Ground Currents in a Venue that might have more than one Ground? (e.g., Lighting, PA, Monitors, Stage, House, 3 phase A/C etc...???
Greetings, Jonathan. Once you gather a bunch of electronic equipment, each with its own connection to AC and ground, it's almost inescapable that a potential will exist between some of the metal parts. This potential is evident in the form of shocks of varying severity, as you noted. It would seem that connecting the metal chassis, stands, etc. to earth ground would solve all the problems, but due to the randomness of the circuitry within the gear and the wiring of receptacles, this is not always the case. The one sure way to eliminate this hazard would be to connect all metal-bodied gear with a single earth ground wire, thus eliminating the potential between each item.
Thanks for answering my questions!
I love music science, it's the best
Amen, ЯроВолК :)
I use to have a photo of my SG plugged into a BF bassman with a two prong power cord and a voltmeter across the bridge and tail piece to ground , If I flipped the ground switch on the amp you can see 120vAC applied to the bridge stop ; If I were to touch a microphone whose base was grounded it would complete the circuit .
........and your screen name would become a reality.......Lost. More than a few performers have been fried in this manner. Thank heavens you tested it and (hopefully) solved the problem with a polarized, chassis-grounding power cord......after resolving the dead-short-to-chassis issue (shorted death cap??) within the amp.
I replaced it with a 3 prong cord !
That definitely sounds like a step in the right direction.
Lost, an amp with a leaky "death cap" will usually trip a GFCI outlet. A smart tactic is to plug any newly acquired amp or other electrical/electronic device, power tool, etc into a code-compatible kitchen or bathroom outlet (GFCI outlets are typically mandated) to see if the amp trips the built-in breaker. Probably not a bad idea to use a GFCI equipped power strip for both the onstage equipment AND the house mixer/monitor mixer. It's not a cure-all but it might alert you in advance to a serious shock hazard, or automatically shut off the power so you don't just stand there with seized-up, frozen muscles as you continue to fry....
Here in India we have concrete/cement/tiled floors.
In my case, the amp has a three pin supply cord, it's plugged into a "spike guard" that shows you if the connection is grounded, and it was, but I still got shocked.
Wearing shoes now to play the guitar, and touching no grounded metal objects with the guitar in my hands.
A wise move, Yati. As you found out, being grounded has its drawbacks.
@Uncle Doug
I started playing guitar very recently ,
Bought new guitar and amp
Since its 2020 I had no worries about getting electrocuted
Surprisingly the amp i bought
(marshall code 25watt)
Came with a 2 prong power cord
I didn't thought much of it ,
Didn't know what 3 prongs did
So when I start playing nothing initially happened
I was sitting on the bed with no carpet or shoe for that fact , in solid ground
I got very small but noticeable zap from the guitar after playing it for 10 minutes
I bought a 3 prong power cable and started playing on carpet with leather shoes
I don't think I have been zapped but I got so paranoid the first time , now I get nervous after playing it for 10 minutes and stop after 10-15 minutes just to not get shocked again
If the 3-wire cord was properly installed, Z, you have nothing to fear.
@@UncleDoug To be honest i don't know if the chord works properly or not
But why would a new 3 prong cable not work properly?
Though I'm kind of curious
Is it possible that a 3 prong socket
(which the power cord goes into)
Does not actually have a ground path?
And the 3rd hole is just for the fit and aesthetics?
I'm so paranoid
(Partly because I Don't have any prior experience to electric guitars or something like this)
I'm considering buying a wireless transmitter to calm myself but its extremely expensive
Even if it doesn't shock me , im always on the edge ready to jump up if i feel anything
You cannot play music like that..
:' l
Sound guys should, must watch this video. Specially when you have a humm/buzz problem and the solution is… 🥁 GROUND LIFT!
Thanks for you input, CC :)
Very well explained
Thanks, Paul :)
I am here learning, because yesterday I was playing my guitar into a Fender 1960 amplifier, then someone knocked the door, and when I putted my hand into the door handle Baaaang! !!!! what a Shock!!
Since the doorknob was probably not grounded, the shock may have just been static electricity. Get a voltmeter and measure for voltage potential between your guitar strings (plugged into amp as if playing) and an earth ground (i.e. a cold-water faucet).
Doug, for many years I use EMG active pickups. Per documentation "EMG Pickups are shielded internally and DO NOT require string
grounding. This greatly reduces the possibility of reverse
polarity shock from microphones and other equipment." Does it mean that I have absolutely no "shock issues" discussed in this video? Thanks.
I am not familiar with the peculiarities of EMG pickups, Pavel, and wonder how a circuit can be completed between the pickups and the amplifier without a two-wire connection. Secondly, I doubt that whatever voodoo is transpiring will eliminate ALL shock issues. My advice is to always follow safe practices when dealing with electronic equipment, regardless of "documentation" :)
And further to this - sticking your hand in amps as Uncle Doug has warned us about but I still got zapped the other day on an amp that I built. I turned in on briefly to check which way the power switch went as I was mounting the amp upside down in a cab and after turning it off I went to turn the switch 180 degrees and shorted across the terminals with my finger and got a nice little buzz. The amp had no speaker mounted and I wonder if this didn't allow the cap's to discharge?
Sorry you got zapped, Freddy. Hopefully your warning will save others from the same unpleasant experience. Generally, the filter caps drain through the (hot) tubes. Since your tubes had no time to heat up, the caps would require more time to discharge. It's always a good idea to manually discharge them with a 100 ohm 10W resistor just to play it safe. You're lucky it was just your hand. If you contact high voltage with both hands, the current will pass through the heart....not a good idea. Hence the rule, one hand in the pocket when working on a live chassis.