You do a really good job of explaining these things in laymen's terms to us newbies Brad. Much appreciated for the work that you do and how you teach us all.
Love watching you do this stuff. When you were soldering in the choke around the 19:00 mark I had a flashback to my Army electronics school days and the sergeant yelling "NO WATCHES, RINGS OR DOG TAGS!" at us constantly and I had a bit of a cringe when I saw your rings on LOL
Your Sergeant has explained to me why when my wedding ring hit the power supply output on my 100 watt Acoustic 4-10s amp, I saw a flash that looked like a nuclear bomb going off and ended up missing 100 bucks worth of gold off the ring.
EXCELLENT post, Brad. LOVE this stuff. I know that you're enduring or at least HAVE endured past personal issues but THIS video is the reason that I am a follower of yours.
HOLY SHIT MAN! Brad your blowing my mind with this stuff. I give you all the props when it comes to this science behind this stuff. Your the amp science guru! All the credit to you! Wonderful video!
I'd just like to point out something, courtesy of Mr. Blencowe: The Valve Wizard "Many Fender-derived amps use a choke-capacitor (LC) filter to supply the power valve screen grids. An LC filter is a second-order filter, so it provides steeper attenuation of ripple than an RC (first order) filter, and a choke has only a little DC resistance so it doesn't drop much DC voltage. Fender was interested in maximising voltage in order to maximise clean output power. These days people like to overdrive their amps, so there is no need to squeeze out every last watt of clean power, so many amps use RC filtering for the screen grids, which is much cheaper than using a choke. The exact value of choke is not critical, but it muct be remembered that an LC filter also resonantes at its corner frequency, which is given by: f = 1 / (2 pi sqrt[LC] ) If this is not well damped then it can cause the supply voltage to 'ring' when triggered by certain notes or rhythms, so it is usually best to keep the resonant frequency below 10Hz, out of the audio range. This will require a capacitor larger than: C = 1 / ( L × [2 pi f]^2 ) Since smoothing capacitors are most readily avalable in the range of 10uF to 100uF, you usually see chokes in the range of 20 to 2 henrys."
Man, of all the books I have, “designing tube preamps for guitar and bass” is my absolute favourite. I’ve bought a number of tube amp books over the years, but anytime I’m having to solve a problem, I always revert to that book because any answer I need is in there, and is usually listed in the table of contests too, so it’s easy to find. I actually have the book on my bedside table at the moment, I’m about to do a big makeover of a little amp and I’m going through the book working out what mods I’m going to do, what value resistors and caps, etc. etc. such a great resource.
The whiteboard explanation of a choke/inductor and capacitor is a better explanation of either than I ever got going to school for electrical engineering. I wish I had this video 10 years ago!
I literally just added a choke on my latest amp build last week! Excellent video Brad 😊 choke makes such an awesome difference. Cleans up the power supply and I found hat in my amp it tightened up the response and added clarity. Oh, made the amp quiet as well! Have an awesome day dude!
@@TheGuitologist Ah thanks man! Very kind of you 🙏 Yep - on my way for sure! I have another two builds planned already! Its addictive! 😃 Have an awesome day!
U will never get rid of the noise whith the transformer placement. This is why placement and orientation matters . Great job on explaining chokes . Really enjoy your videos
Enjoyed the white board explanation man! I hope you’ll continue with that kind of break down in future videos. I get kinda cross eyed with schematics some times but watching someone draw things out like that while explaining in simple terms is great!
Early on when tube amps had electrodynamic speakers they did not use a choke... well, they did, but it was the magnet coil of the electrodynamic speaker that acted like the choke. Once permanent magnet speakers became available the need for a choke arose.
There's something to be said for keeping the originality, but I'll take function over form any day. Changing the caps and adding the choke sure blows originality out of the water. For all the times you've pulled the chassis you should have added a 1/4" jack and plug for the speaker connection. That's not original but it beats the hell out of de-soldering it.
awesome video! Even an amateur tinkerer like me can understand. The before-after noise comparison didn't sound all that different but when you factor in the increase in wattage it actually is a lot quieter! and now I know a choke kind of does what I thought it would do, there's no secondary winding to grab the magnetic field so the primary winding grabs some back? or something? so it has an electrical cushioning effect. well, the important part is it makes the amp louder and less noisy and increases your rectifier tube lifespan.
You are a lot more knowledgeable about this than I am, when you installed the Choke, I see that both the power transformer and output transformer are both facing the same direction, I always heard one much place the in opposite facing direction, might that have been one of the sources to the hum?
I most often use 2 chokes, one right off the rectifiers, and another one between the first 2 caps. Doing this you can use a smaller value of inductance on the first choke, as long as the current rating is sufficient.
Very nice and visual explained! I calculated my self nearly to death in my studies about filters on university, and your video explains it all clearly without using eny Formula. Well done sir!
I feel like if concepts are understood roughly first, the equations make way more sense. Inductors is some tough math though. Everything has a time component. Best understood with graphs.
As with all things guitar, gear forums will worship at the altar of the choke as some magical tone shaping mod when in reality it just lowers noise/hum/hiss
In this case, I don't think the hum was lowered. I think that was already about as low as we were able to get it, but a choke will lessen wear on other components in the power section.
It's also a bit of a conditioner is the way I look at them, lowering the noise floor is a benefit. I'm going to listen to what brads points are just to see what he has to say I don't know everything yet🤣
@@TheGuitologist You're wicked smart Brad ! Thanks for the layman breakdown. I get the gist but the serious technicalities is what I lack. I just haven't learned to read schematics yet. The experiential knowledge you have is invaluable. Really appreciate it. 👍✌
4:47 - The filter in the middle is a three pole filter - so the out-of-band roll-off will be steeper compared to the two pole below. You'll get something like 20dB of attenuation per decade (freq) for each L or C. Therefore the pi filter in the middle should get you (at least) 60dB of attenuation out somewhere around 60Hz (assuming the passband ends at 6Hz) whereas the two element filter at the bottom would be in the ballpark of 40dB a decade out. So, the pi filter in the middle is not only cheaper and lighter - it's fundamentally better at rejecting those pulses coming off of the rectifier tubes. "Handbook of Filter Synthesis" - A. Zverev "Microwave Filters, Impedance Matching and Coupling Structures" - Matthaei, Jones, & Young (I'm an engineer in real life - 24 years in Silicon Valley)
First time I saw a configuration similar to Fig. 30.1G was in the schematic for a Hammond spinet organ similar to the one from which a Rola field coil speaker had been pulled; the field coil was between circuit ground and the transformer's center tap. If the power transformer is designed to provide, say, 90V more than what you want at your output tubes' plates, and you must use a field coil speaker, this is an elegant way to simultaneously power the field coil and filter mains hum.
I just loved the videos you made for this amp. I never get the chance to work on tube based circuits so to me anyways, this type of stuff is just great. I do have some schooling on tube circuits because back in the 70s they were still teaching both types of circuits in high school (3 yrs) but tubes were definitely on their way out. Except for guitar amps and some other exceptions. I don't want to sound like a frickin' 62 yr old fan boi, but I do dig your show. Great Job!
Hammond makes some good parts and are really sought after in amps, especially Hammond transformers from the 70s. I have a traynor that has huge Hammond transformers
Spot on treatise of the choke function! Given the added advantage we now have of extended component capacitance (and voltage ratings), the choke, these days, adds little but weight. Folks did use that Amp as was, after all. ;-) That experiment DID show useful, IMHO.
Howdy. Nice. Using Solid State rectification the choke may be replaced with large capacitors. Yes. But the transformer current becomes spiky. Spiky current produces lots of reactive power. It may happen that the transformer VA rating is too low. Could explain why burnt out power transformers are sometimes experienced. Tube rectifiers don't tolerate spiky current. The spec.s will tell the largest allowable input capacitor. More DC filtering is needed and this is why chokes are mandatory. High Regards.
That was one of the most informative vids you've ever produced Brad! My one question for you is: what do you use to test inductance? I've been needing to get an inductance tester primarily for car audio inductor testing, but I've been hesitant to purchase one of the cheap ones which are all made and sold in China. It seems they're all I can find or perhaps those are all that's available.
Excellent discussion, Thanks. You have a great teaching style that takes a complex subject and makes it very easy to understand. Just like my other amp guru Uncle Doug. Oh, and I'll soon be building the Bias probe, probably two of them for push/pull amps.
Funny i just acquired a bunch of tvs with plenty of chokes... great timing as per usual brad.. yoy and Uncle Doug just have a knack for answering whats on my mind lol
Hey there can i suggest to you that you ignore these critics if they know so much why are they watching you ???? really i think you are good at what you do and very good at explaining the works !!!!☮👏🏴☠️
Great information having a problem with mine on my old house tube amps need replacing (heat) finding parts not easy to get matching part numbers thanks for this info
in this case, hum wasn't affected. The choke was still a good upgrade though because the rectifier and everything else in the power supply will be less stressed because of the choke. In other cases, the affect on hum may be more pronounced.
@@TheGuitologist Oh i see, thanks for your kind answer. I have a 5F1 clone and was considering adding a choke to reduce 50hz hum but i probably will learn to live with it as it is not as bad. Cheers!
Great video, Brad. A choke is a must in a tube rectifier circuit. Any decent amp would have a Pi filter on the B+. I don't know why an engineer would choose an LC over a Pi, other than cost reduction. The amount of ripple and IMD reduction provided by that second cap is certainly audible.
Trying many amps hasn't quenched my dream of experiencing Univox and Teisco. They're nearly impossible to find in France or Europe. I recently had a lot of fun with a Univox PHZ-1 phase shifter (relabelled BST LM-200 in France). If you'd like to give it a shot, my experimentations are on my channel.
Not sure if it has been mentioned, but you are at almost 30mA on one channel so that is 60mA for both. The choke is rated at 50mA, did you reach inside and feel if the choke is getting hot?
I usually add a solid state rectifier if I'm trying to up the B+. I'm of the opinion that the "sag" that you get from tube rectifiers is overrated. I believe what people hear when they swap out the tube rectifier for solid state has more to do with the B+ change than actual "sag" at any rate. Eddie Van Halen used a variac to lower the B+ and get that same squishy sound. Chokes are a nice way to get some extra volts as well.
If you learn about grounding schemes you can turn up the vol to 10 max and you shouldn't hear any white noise hiss. The new grounding schemes you should look into because you can convert older fender amps and marshall amps so they don't make any hiss when max vol at 10 with nothing plugged into the amp. EVH took out his chokes in his marshalls to get more plate voltage. I'm not sure if remove chokes increases the plate voltage but it "increases" the current to the power tubes since the choke is not consuming soaking up the current to the bias voltage, cathode current and plate current. If you take your DVM meter and press the MAX button to measure the max voltage and max current with the CHOKE and without the choke, when you're strumming the guitar very hard which will draw more current from the rectifier tube and the choke will lag consume the current which gives you that sag. I rather have seen the max voltage/max current with the choke and without the choke when strumming the guitar very hard to measure that test.
Many years ago I sent one of my amps to be worked on at a then well known facility who used to sell mod kits. When I got it back it was working but they removed the original choke and substituted them for some resistors; if I remember correctly. I heard it would do the same thing but makes me wonder if the outfit wasn’t that honest and they just confiscated my amp’s choke for their use/gain. Later on I had to buy another choke and get it installed by another tech.
@@highpath4776 I had a guitar shop charge me extra on my guitar after having pick ups swapped. Because he took It on himself to replace my pots. Why? What's wrong with my pots? They were bad. Can I have em back? No. Why would you want them? I'm out of this place. Started trying to do stuff myself after that.
I don't know if it's just the compression in the video but in the comparison section I heard only a VERY slight reduction in hum that was accompanied by a VERY slight increase in hiss, didn't seem to be very effective at all and the overall noise level seemed to be the same. What's up with that?
I think you are correct. I believe in this particular amp, the noise had already been reduced about as much as it possibly could be reduced using other means of virtual center taps and lead dress, ground buss, etc. I did a TON of work to get the amp this quiet. Even with the lack of improvement on hum, which was already pretty damn low, I still think a choke is good for the amp. All the power section components will not wear as fast or be as taxed by inrush currents.
Great video, Brad. I like the idea of the cathode hookup on the bias probe. Would you know the benefits of using the 30.1F vs 30.1G wiring or vice versa?
All power supplies regardless of their wattage benefit from capacitive/inductive filtering, the flatter the rectified and filtered output voltage the closer it is to pure DC. LC filtering does this type of thing very well.
Very true . The sought after early Vox AC4 used a 1 k 5W wirewound ceramic resistor which is also an inductor . I haven't heard of anyone replacing the 1K 25W wirewound resistor fitted in the Fischer Trainwreck either that resides in place of a choke . WW resistors are actually inductors , nothing more than a coil of wire wrapped around a core .
Hello Friend. I want to say that placing all electrolytic capacitors in one place with a common ground and pulling long anode wires to each stage is not the right solution, this is the worst thing you can think of. Move each capacitor as close as possible to the cascade that it feeds and place its ground in the same place near the cathode resistor that it supplies to the cascade. This is a unified system ... And you will be happy, noises and pickups will noticeably decrease or disappear altogether.
At around the 15:00 minute mark, it took me a second to realize your diagram was not a dead guy and you weren't going to give a warning about voltages. Guess I need some more coffee...
sorry brad but it seems in flat out mode you're on the threshold of motorboating . it sounds like some tube needs more dc isolation . i put a choke on a marshall class 5 ( single 6bq-5 power tube) with great result now there's no hum but we can only hear noise from the preamp tube.
I have a question, please dont humiliate me, lol. I truly know just about nothing about tube amps other than I have one and I like it. It's a late 80's Peavy VTM 60. Spent the 10 years before my 10 years with her in an unheated New England horse barn, I have NEVER done any tlc. The volume is dropping out now when I run dirt pedals into the clean channel, I think I should just swap out all the tubes in one wack. I can do that right? If not changing anything, just putting back in it what it is supposed to have, I dont need a tech to do it right? Just pull the old, plug the new. I have heard of "rebiasing", and "dont do this yourself you can get hurt", anything to that line of reasoning? I just want the thing to keep working, although if I can get more DIRTY right from the amp I would love to know what tube replacement would help.
Of course you CAN do anything you want. But an amp that old with no one looking at it in over 20 years... It will need the caps checked and all the jacks, switches, sockets, and pots cleaned and lubed, it'll need the solder joints gone over thoroughly and reflowed, it'll probably need new output tubes, but perhaps not. Hard to say. Sound dropping out is a sign of something intermittent, like the aforementioned dirty socket, bad solder joint, etc. These are all common things. That's a great amp. Take care of it and it'll take care of you. 80s Peaveys are bulletproof!
@@TheGuitologist thanks for getting back to me! Yes Brad, I s'pose your right, I need to stop being so cheap and get the ol Peavy the care it deserves. I thought I was somewhat frugal, guess I was being a dick,lol.
Say you did build a guitar amp with a choke input filter, where would you wire in a bleeder resistors say the choke does not arc when you turn the amp off? What value and wattage resistor might you use? I actually did build one with a choke input and it’s awesome, but I do have the arc issue.
Your 'friend' Steve that supplied you with that awesome RCA Radiotron designers Handbook...wouldn't happen to be Steve Melkesethian of Angela Instrument ( well known tube amp guru and purveyor of related documentation and components) now would it?? 😁😉
It seems as if you know something I don’t? You did remind me I still need to unpack those boxes of catalogs. I’ve had so much on my plate and my mind. I’m sorry I’ve let you down on opening those in a timely manner. They’re still on my list.
@@TheGuitologist Oh yeah...Ive watched those...He's aCool dude....that book is an invaluable resource for tube amp techs....hard to find these days..Steve at Angela instrument used to offer them from time to time but they would always be gone by the time I got his print catalog..back in the day before the 'Web'..Cheers!
@@TheGuitologist Hey Brad..no worries ! You have had a lot on your plate no expectations on this end. You helped me out by accepting my collection and providing it a safe and worthy home..beyond that I was hoping you might find some cool and maybe helpful/usefull items in the contents. I still have a pretty good amount with me here in Alaska that you are welcome to have if/when you feel ready for it...but I think you should peruse the other boxes first as you may not want any more ..cause it's a lot of stuff to digest and store,etc. So relax dude..we are good..I must apologize for the way that stuff was packed. It is in a semblance of order but pretty messy and since I didn't have access to a computer at the time, my handwritten letter and notes are probably difficult to read/I interpret cause my handwriting sucks.. sorry bout that..let me know if you have any questions and I'll try and sort it out..it's been a couple years so I may have forgotten some stuff. Cheers!
You do a really good job of explaining these things in laymen's terms to us newbies Brad. Much appreciated for the work that you do and how you teach us all.
Fantastic video and very informative. Chokes were always a kind of a mystery to me but no longer.
Awesome white board section, Brad! Editing was excellent and you explained that all so well!
Thanks Jon.
I have learned so much from this channel. I feel like I’m almost ready to build me own amp ⚡️ 🎸
Definitely informative! You filled in a gap in my knowledge that I haven’t gotten around to yet. Been wondering about chokes lately. Thanx!
Thanks man. Seriously appreciate the refresher choke course. you Just saved me so much time.
Glad you benefited from it.
Love watching you do this stuff. When you were soldering in the choke around the 19:00 mark I had a flashback to my Army electronics school days and the sergeant yelling "NO WATCHES, RINGS OR DOG TAGS!" at us constantly and I had a bit of a cringe when I saw your rings on LOL
best ignore stupid advice...regardless of were or who it came from
@@trillrifaxegrindor4411 ?
Your Sergeant has explained to me why when my wedding ring hit the power supply output on my 100 watt Acoustic 4-10s amp, I saw a flash that looked like a nuclear bomb going off and ended up missing 100 bucks worth of gold off the ring.
This is great info. Commenting to goose the channel algorithm.
EXCELLENT post, Brad. LOVE this stuff. I know that you're enduring or at least HAVE endured past personal issues but THIS video is the reason that I am a follower of yours.
HOLY SHIT MAN! Brad your blowing my mind with this stuff. I give you all the props when it comes to this science behind this stuff. Your the amp science guru! All the credit to you! Wonderful video!
I'd just like to point out something, courtesy of Mr. Blencowe:
The Valve Wizard
"Many Fender-derived amps use a choke-capacitor (LC) filter to supply the power valve screen grids. An LC filter is a second-order filter, so it provides steeper attenuation of ripple than an RC (first order) filter, and a choke has only a little DC resistance so it doesn't drop much DC voltage. Fender was interested in maximising voltage in order to maximise clean output power. These days people like to overdrive their amps, so there is no need to squeeze out every last watt of clean power, so many amps use RC filtering for the screen grids, which is much cheaper than using a choke. The exact value of choke is not critical, but it muct be remembered that an LC filter also resonantes at its corner frequency, which is given by:
f = 1 / (2 pi sqrt[LC] )
If this is not well damped then it can cause the supply voltage to 'ring' when triggered by certain notes or rhythms, so it is usually best to keep the resonant frequency below 10Hz, out of the audio range. This will require a capacitor larger than:
C = 1 / ( L × [2 pi f]^2 )
Since smoothing capacitors are most readily avalable in the range of 10uF to 100uF, you usually see chokes in the range of 20 to 2 henrys."
Merlin is the man. Aiken has some good articles on this stuff too. Great resources.
Man, of all the books I have, “designing tube preamps for guitar and bass” is my absolute favourite. I’ve bought a number of tube amp books over the years, but anytime I’m having to solve a problem, I always revert to that book because any answer I need is in there, and is usually listed in the table of contests too, so it’s easy to find. I actually have the book on my bedside table at the moment, I’m about to do a big makeover of a little amp and I’m going through the book working out what mods I’m going to do, what value resistors and caps, etc. etc. such a great resource.
The whiteboard explanation of a choke/inductor and capacitor is a better explanation of either than I ever got going to school for electrical engineering. I wish I had this video 10 years ago!
Awesome, informative video!! I'm all choked up!
I literally just added a choke on my latest amp build last week! Excellent video Brad 😊 choke makes such an awesome difference. Cleans up the power supply and I found hat in my amp it tightened up the response and added clarity. Oh, made the amp quiet as well! Have an awesome day dude!
You’re on your way to being an amp builder, Jay. Loved your build video.
@@TheGuitologist Ah thanks man! Very kind of you 🙏 Yep - on my way for sure! I have another two builds planned already! Its addictive! 😃 Have an awesome day!
U will never get rid of the noise whith the transformer placement. This is why placement and orientation matters . Great job on explaining chokes . Really enjoy your videos
Love this! As an old RADAR Tech the technical aspect enthralls me.
I learned some more from you man, thanks for sharing....I appreciate you taking time to use the simpler explanations as well as the technical bits.
Enjoyed the white board explanation man! I hope you’ll continue with that kind of break down in future videos. I get kinda cross eyed with schematics some times but watching someone draw things out like that while explaining in simple terms is great!
The "chokes explained on the whiteboard" section is great! It could stand on its own as a broken out video.
I’ll put it on Channel 2
Early on when tube amps had electrodynamic speakers they did not use a choke... well, they did, but it was the magnet coil of the electrodynamic speaker that acted like the choke. Once permanent magnet speakers became available the need for a choke arose.
You're never a letdown. 10w!
We got there eventually. Full dissipation.
Thanks Brad for showing us how a chock works, please do more of these videos.
There's something to be said for keeping the originality, but I'll take function over form any day. Changing the caps and adding the choke sure blows originality out of the water. For all the times you've pulled the chassis you should have added a 1/4" jack and plug for the speaker connection. That's not original but it beats the hell out of de-soldering it.
That was excellent. Best choke explanation on youtube.
awesome video! Even an amateur tinkerer like me can understand. The before-after noise comparison didn't sound all that different but when you factor in the increase in wattage it actually is a lot quieter! and now I know a choke kind of does what I thought it would do, there's no secondary winding to grab the magnetic field so the primary winding grabs some back? or something? so it has an electrical cushioning effect. well, the important part is it makes the amp louder and less noisy and increases your rectifier tube lifespan.
You are a lot more knowledgeable about this than I am, when you installed the Choke, I see that both the power transformer and output transformer are both facing the same direction, I always heard one much place the in opposite facing direction, might that have been one of the sources to the hum?
I most often use 2 chokes, one right off the rectifiers, and another one between the first 2 caps. Doing this you can use a smaller value of inductance on the first choke, as long as the current rating is sufficient.
Very nice and visual explained! I calculated my self nearly to death in my studies about filters on university, and your video explains it all clearly without using eny Formula. Well done sir!
I feel like if concepts are understood roughly first, the equations make way more sense. Inductors is some tough math though. Everything has a time component. Best understood with graphs.
Really good job with the choke lecture. Can see all the effort that went in. Also very good amp stuff, good vibes and all.
This one was very good there Brad.
As with all things guitar, gear forums will worship at the altar of the choke as some magical tone shaping mod when in reality it just lowers noise/hum/hiss
Well duh !🤣😋
In this case, I don't think the hum was lowered. I think that was already about as low as we were able to get it, but a choke will lessen wear on other components in the power section.
It's also a bit of a conditioner is the way I look at them, lowering the noise floor is a benefit.
I'm going to listen to what brads points are just to see what he has to say I don't know everything yet🤣
@@TheGuitologist
You're wicked smart Brad !
Thanks for the layman breakdown.
I get the gist but the serious technicalities is what I lack. I just haven't learned to read schematics yet. The experiential knowledge you have is invaluable. Really appreciate it. 👍✌
Dude, forget the Variac or Phillips 6CA7's... THIS was the secret to Eddie Van Halen's brown sound!
I know chokes really well but your video was fun to watch!
That whiteboard explanation was so nice ! :D
Oh Sh!+ ... I just went to school. This is the best vid. Thank you.
4:47 - The filter in the middle is a three pole filter - so the out-of-band roll-off will be steeper compared to the two pole below. You'll get something like 20dB of attenuation per decade (freq) for each L or C. Therefore the pi filter in the middle should get you (at least) 60dB of attenuation out somewhere around 60Hz (assuming the passband ends at 6Hz) whereas the two element filter at the bottom would be in the ballpark of 40dB a decade out. So, the pi filter in the middle is not only cheaper and lighter - it's fundamentally better at rejecting those pulses coming off of the rectifier tubes. "Handbook of Filter Synthesis" - A. Zverev "Microwave Filters, Impedance Matching and Coupling Structures" - Matthaei, Jones, & Young (I'm an engineer in real life - 24 years in Silicon Valley)
First time I saw a configuration similar to Fig. 30.1G was in the schematic for a Hammond spinet organ similar to the one from which a Rola field coil speaker had been pulled; the field coil was between circuit ground and the transformer's center tap. If the power transformer is designed to provide, say, 90V more than what you want at your output tubes' plates, and you must use a field coil speaker, this is an elegant way to simultaneously power the field coil and filter mains hum.
I just loved the videos you made for this amp. I never get the chance to work on tube based circuits so to me anyways, this type of stuff is just great. I do have some schooling on tube circuits because back in the 70s they were still teaching both types of circuits in high school (3 yrs) but tubes were definitely on their way out. Except for guitar amps and some other exceptions. I don't want to sound like a frickin' 62 yr old fan boi, but I do dig your show. Great Job!
Hammond makes some good parts and are really sought after in amps, especially Hammond transformers from the 70s. I have a traynor that has huge Hammond transformers
Very informative Brad. Thank you for explaining this to someone who has a keen interest in Valve Amps.
Spot on treatise of the choke function!
Given the added advantage we now have of extended component capacitance (and voltage ratings), the choke, these days, adds little but weight. Folks did use that Amp as was, after all. ;-)
That experiment DID show useful, IMHO.
Hey Brad this is a great topic you are a really good teacher keep it up!
Great serial and i like this video as well, thx for sharing and helping musicians.
Great video, Brad. Loved the whiteboard breakdown. Really brought me back to the classroom.
Great series on this amp!
Great Video Brad! Good explanation of chokes.
Howdy. Nice.
Using Solid State rectification the choke may be replaced with large capacitors. Yes. But the transformer current becomes spiky. Spiky current produces lots of reactive power. It may happen that the transformer VA rating is too low. Could explain why burnt out power transformers are sometimes experienced.
Tube rectifiers don't tolerate spiky current. The spec.s will tell the largest allowable input capacitor. More DC filtering is needed and this is why chokes are mandatory.
High Regards.
No demo????
See the Part 1 and Part 2 videos of this amp for jamming demos.
Excellent full featured content. Thanks Brad.
That was one of the most informative vids you've ever produced Brad! My one question for you is: what do you use to test inductance? I've been needing to get an inductance tester primarily for car audio inductor testing, but I've been hesitant to purchase one of the cheap ones which are all made and sold in China. It seems they're all I can find or perhaps those are all that's available.
Maybe you can build one…
Awesome video Brad !!
holy cow what a legend
Excellent discussion, Thanks. You have a great teaching style that takes a complex subject and makes it very easy to understand. Just like my other amp guru Uncle Doug. Oh, and I'll soon be building the Bias probe, probably two of them for push/pull amps.
Add a lead on the cathode to measure plate voltage on cathode biased amps.
@@TheGuitologist Yes, I saw that. Thanks.
Funny i just acquired a bunch of tvs with plenty of chokes... great timing as per usual brad.. yoy and Uncle Doug just have a knack for answering whats on my mind lol
Great episode..vast improvement..love the use of the old tech books....
Hey there can i suggest to you that you ignore these critics if they know so much why are they watching you ???? really i think you are good at what you do and very good at explaining the works !!!!☮👏🏴☠️
I have 2 accounts on TH-cam - Guitologist and Guitologist Channel 2.
Nicely done.
Great information having a problem with mine on my old house tube amps need replacing (heat) finding parts not easy to get matching part numbers thanks for this info
So, hum and noise levels wasn´t reduced at all? or am i missing something? I do not hear any improvement after the modification. Am i right?
in this case, hum wasn't affected. The choke was still a good upgrade though because the rectifier and everything else in the power supply will be less stressed because of the choke. In other cases, the affect on hum may be more pronounced.
@@TheGuitologist Oh i see, thanks for your kind answer. I have a 5F1 clone and was considering adding a choke to reduce 50hz hum but i probably will learn to live with it as it is not as bad. Cheers!
Great video, Brad. A choke is a must in a tube rectifier circuit. Any decent amp would have a Pi filter on the B+. I don't know why an engineer would choose an LC over a Pi, other than cost reduction. The amount of ripple and IMD reduction provided by that second cap is certainly audible.
Thanks Brad!
Trying many amps hasn't quenched my dream of experiencing Univox and Teisco. They're nearly impossible to find in France or Europe. I recently had a lot of fun with a Univox PHZ-1 phase shifter (relabelled BST LM-200 in France). If you'd like to give it a shot, my experimentations are on my channel.
You always outdo yourself
Excellent video.
Damn I was worried that Brad might be in danger of going off the deep end.
Now it's confirmed...
Damn dude is choking his chicken on TH-cam.
I’ve yet to choke an amp so this should be informative.
Great job Brad, very informative.
Not sure if it has been mentioned, but you are at almost 30mA on one channel so that is 60mA for both. The choke is rated at 50mA, did you reach inside and feel if the choke is getting hot?
The EGO power blower ad was pretty cool and watched it all. I sent you some money Brad... ;)
I usually add a solid state rectifier if I'm trying to up the B+. I'm of the opinion that the "sag" that you get from tube rectifiers is overrated. I believe what people hear when they swap out the tube rectifier for solid state has more to do with the B+ change than actual "sag" at any rate. Eddie Van Halen used a variac to lower the B+ and get that same squishy sound. Chokes are a nice way to get some extra volts as well.
Excellent White Board demo Brad ... Could you do one about the'' Birds and the Bees'' ... Lol ... Great vid as usual ... Thx for sharing ...
I'll need to borrow your wife for the other thing. I'm sure you won't mind.
@@TheGuitologist I'll send her right up ... Lol ...
A quick tube tickling, she’ll be right back, good as new.
If you learn about grounding schemes you can turn up the vol to 10 max and you shouldn't hear any white noise hiss. The new grounding schemes you should look into because you can convert older fender amps and marshall amps so they don't make any hiss when max vol at 10 with nothing plugged into the amp. EVH took out his chokes in his marshalls to get more plate voltage. I'm not sure if remove chokes increases the plate voltage but it "increases" the current to the power tubes since the choke is not consuming soaking up the current to the bias voltage, cathode current and plate current. If you take your DVM meter and press the MAX button to measure the max voltage and max current with the CHOKE and without the choke, when you're strumming the guitar very hard which will draw more current from the rectifier tube and the choke will lag consume the current which gives you that sag. I rather have seen the max voltage/max current with the choke and without the choke when strumming the guitar very hard to measure that test.
When this video popped up I had to ask myself what this amp ever did to you?
Really interesting video! I learnt a lot thank you so much 😊
Love the artwork Brad 😅, I might have paid more attention in electronics class had you been my teacher
What an amazing book 🤘🤘🤘!!
Many years ago I sent one of my amps to be worked on at a then well known facility who used to sell mod kits. When I got it back it was working but they removed the original choke and substituted them for some resistors; if I remember correctly. I heard it would do the same thing but makes me wonder if the outfit wasn’t that honest and they just confiscated my amp’s choke for their use/gain. Later on I had to buy another choke and get it installed by another tech.
Stuff like that happens. Maybe the choke was open?
@@TheGuitologist Old Parts should always be returned to the person commissioning the repair unless they say otherwise.
@@highpath4776 I had a guitar shop charge me extra on my guitar after having pick ups swapped. Because he took It on himself to replace my pots. Why? What's wrong with my pots? They were bad. Can I have em back? No. Why would you want them?
I'm out of this place. Started trying to do stuff myself after that.
I don't know if it's just the compression in the video but in the comparison section I heard only a VERY slight reduction in hum that was accompanied by a VERY slight increase in hiss, didn't seem to be very effective at all and the overall noise level seemed to be the same. What's up with that?
I think you are correct. I believe in this particular amp, the noise had already been reduced about as much as it possibly could be reduced using other means of virtual center taps and lead dress, ground buss, etc. I did a TON of work to get the amp this quiet. Even with the lack of improvement on hum, which was already pretty damn low, I still think a choke is good for the amp. All the power section components will not wear as fast or be as taxed by inrush currents.
I was wondering, what causes chasse buzz, if I spelled that right? When you pushed up on it, it stopped buzzing. Cool video, by the way.
Great video, Brad. I like the idea of the cathode hookup on the bias probe.
Would you know the benefits of using the 30.1F vs 30.1G wiring or vice versa?
I'm going to add one to my existing probes.
Woo Hoo like number 305! Great and informative video, as usual. Keep up the great work.
Great video Thank you
Do you think you'll ever bring back spf?
When the tyranny ends, I will.
consensus on the street is every amp is improved by adding a choke. I suspect this is false, especially in lower wattage amps
All power supplies regardless of their wattage benefit from capacitive/inductive filtering, the flatter the rectified and filtered output voltage the closer it is to pure DC. LC filtering does this type of thing very well.
Very true . The sought after early Vox AC4 used a 1 k 5W wirewound ceramic resistor which is also an inductor . I haven't heard of anyone replacing the 1K 25W wirewound resistor fitted in the Fischer Trainwreck either that resides in place of a choke . WW resistors are actually inductors , nothing more than a coil of wire wrapped around a core .
Hello Friend. I want to say that placing all electrolytic capacitors in one place with a common ground and pulling long anode wires to each stage is not the right solution, this is the worst thing you can think of. Move each capacitor as close as possible to the cascade that it feeds and place its ground in the same place near the cathode resistor that it supplies to the cascade. This is a unified system ... And you will be happy, noises and pickups will noticeably decrease or disappear altogether.
At around the 15:00 minute mark, it took me a second to realize your diagram was not a dead guy and you weren't going to give a warning about voltages. Guess I need some more coffee...
A question ive always wanted to ask
The choked chicken in the thumbnail 😂
16:30 Those are some nice sounding pads in the background soundtrack !! What did you use to get those , Brad?
That’s not my track. It’s from the TH-cam library
sorry brad but it seems in flat out mode you're on the threshold of motorboating . it sounds like some tube needs more dc isolation .
i put a choke on a marshall class 5 ( single 6bq-5 power tube) with great result now there's no hum but we can only hear noise from the preamp tube.
mmm made in Canada, EXCELLENT Simthers EXCELLENT : )
I have a question, please dont humiliate me, lol. I truly know just about nothing about tube amps other than I have one and I like it. It's a late 80's Peavy VTM 60. Spent the 10 years before my 10 years with her in an unheated New England horse barn, I have NEVER done any tlc. The volume is dropping out now when I run dirt pedals into the clean channel, I think I should just swap out all the tubes in one wack. I can do that right? If not changing anything, just putting back in it what it is supposed to have, I dont need a tech to do it right? Just pull the old, plug the new. I have heard of "rebiasing", and "dont do this yourself you can get hurt", anything to that line of reasoning? I just want the thing to keep working, although if I can get more DIRTY right from the amp I would love to know what tube replacement would help.
Of course you CAN do anything you want. But an amp that old with no one looking at it in over 20 years... It will need the caps checked and all the jacks, switches, sockets, and pots cleaned and lubed, it'll need the solder joints gone over thoroughly and reflowed, it'll probably need new output tubes, but perhaps not. Hard to say. Sound dropping out is a sign of something intermittent, like the aforementioned dirty socket, bad solder joint, etc. These are all common things. That's a great amp. Take care of it and it'll take care of you. 80s Peaveys are bulletproof!
@@TheGuitologist thanks for getting back to me! Yes Brad, I s'pose your right, I need to stop being so cheap and get the ol Peavy the care it deserves. I thought I was somewhat frugal, guess I was being a dick,lol.
This will be interesting.
Say you did build a guitar amp with a choke input filter, where would you wire in a bleeder resistors say the choke does not arc when you turn the amp off?
What value and wattage resistor might you use?
I actually did build one with a choke input and it’s awesome, but I do have the arc issue.
Your 'friend' Steve that supplied you with that awesome RCA Radiotron designers Handbook...wouldn't happen to be Steve Melkesethian of Angela Instrument ( well known tube amp guru and purveyor of related documentation and components) now would it?? 😁😉
No, this is my friend Steve Wilson. I’ve made several videos at his studio.
It seems as if you know something I don’t? You did remind me I still need to unpack those boxes of catalogs. I’ve had so much on my plate and my mind. I’m sorry I’ve let you down on opening those in a timely manner. They’re still on my list.
@@TheGuitologist Oh yeah...Ive watched those...He's aCool dude....that book is an invaluable resource for tube amp techs....hard to find these days..Steve at Angela instrument used to offer them from time to time but they would always be gone by the time I got his print catalog..back in the day before the 'Web'..Cheers!
@@TheGuitologist Hey Brad..no worries ! You have had a lot on your plate no expectations on this end. You helped me out by accepting my collection and providing it a safe and worthy home..beyond that I was hoping you might find some cool and maybe helpful/usefull items in the contents. I still have a pretty good amount with me here in Alaska that you are welcome to have if/when you feel ready for it...but I think you should peruse the other boxes first as you may not want any more ..cause it's a lot of stuff to digest and store,etc. So relax dude..we are good..I must apologize for the way that stuff was packed. It is in a semblance of order but pretty messy and since I didn't have access to a computer at the time, my handwritten letter and notes are probably difficult to read/I interpret cause my handwriting sucks.. sorry bout that..let me know if you have any questions and I'll try and sort it out..it's been a couple years so I may have forgotten some stuff. Cheers!
The motorboating at 26:00 - how can I get rid of something like that?
I had a girl once who absolutely needed a good choke
I don't hear a difference before and after . . . what am I missing?
20:50 I hear the same amount of noise before and after... or I am not getting the trick.
I've got a blues junior that I would like to choke...
“Blues Junior” is an interesting pet name for your wife.
Is a O-Henry ? The lowest on that Bar Graph?? 😉