SECRETS of the Fender Bassman - "ABNormal Channel" Mods Unleash the Hidden BEAST!
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- เผยแพร่เมื่อ 21 เม.ย. 2018
- In this video I'll show you how to modify a bone stock 1960s Fender Bassman AC568 or AB165 into a MONSTER amplifier using my "*AB*Normal Channel Mods. I'll show you how to add a Gain Control, a Presence Control, a Midrange Switch, an extra gain stage, and Marshall tone stack all without drilling a single hole or doing anything you can't undo later (not that you'll ever want to).
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Are you under the illusion that a Bassman is or was a guitar amp ? The Bassman was the only bass guitar amp Fender produced in that era. The only thing wrong with it was that it wasn't powerful enough and they came with a pair of 12" speakers that couldn't do the job. You're killing the collectibility of this amp trying to convert it to something it wasn't designed to do. If you want a guitar amp to modify in the same power class as the Bassman then modify a Bandmaster which was intended for guitars.
jchavins i mean you can get these for alot cheaper than most tube amps these days and he made it so you can put it back to stock. And not to beat a dead horse or anything but the first Marshalls wereee based off the 59 bassman don't know if that's been mentioned before haha
if you want a Marshall then just get a Marshall.....This is kind of like putting cheap ceramic Chinese bass pickups on a 57 Strat......don't get me wrong, I really like this channel like the guy said in Jurassic Park----yeah you can do it but should you do it ?
i agree man but for a broke 20 year old a 500 dollar bassman sounds alot better than a 2000 dollar plexi reissue (i have a sovtek mig 50 haha)
Can't wait to see the discussion on this one.
remember: it´s his amp. even if he decides to change it into a let say 4x KT150 power amp, with a nice shielded SMPS to be able to power up these tubes, it would be nothing wrong with that, as it is his amp.
Ha! I am that owner! You read my mind in terms of choices. So pleased with your work! Thankfully, the worst part of the amp seemed to be the enclosure. Imagine the friends I'll make on this end when i get to start playing with it!!
She's a gem. I do recommend getting some plywood and re-cutting that front panel. Other than that, she's ready to rock and roll. Monstrously loud, but you can drive the pre now and turn down, at least. By the way...thanks for being cool and letting me have free reign. It was a fun one to do!
All this video needs is the clip from Young Frankenstein... "What was the name?" "Abby-Normal."
Matthew.... Killlllller mod!! I hope it gives you a lifetime of wickedness... :) \m/, ,\m/
Dude, that amp kills now....Congrats!
Matthew Stecker - awesome amp - get him to sign it before shipping
"...he's using pliers!" I think my favorite thing about this channel (other than your obvious tech and playing skills) is the way you do things to get under the skin of us veteran techs. You know there are veins throbbing in our foreheads as we scream at the screen....especially when you work on SS. The first video I watched on this channel was you working on a Mesa amp with a muting problem. I'm surprised I made it to the end without suffering an aneurysm. Keep on making this one of the best guitar channels on TH-cam.
I feel the same every time Brad undertakes some mechanical bodge. Fortunately my tongue soon repairs itself.
And that I don't mind, for the electronic and musical experimentation we experience isn't available elsewhere.
Dude... Build your own amps. I'm trying to learn 1/2 of what you know and I'm an f'n engineer. DO IT! FFS. You forgot more than I will ever know. Build it.... and they will come. (lol. you see what I did there?) Seriously. You have mad skills.
I agree
Maybe he could do Phil McKnight signature model.....
I could seriously watch the amp mod videos all day. You transformed an amp that I would typically think of a really bland into a spicy little number. That extra gain stage really makes it sing.
Outstanding stuff, Brad!
leo fender will be raising a glass somwhere out there, and muttering "damn" wish i`d done that ,the tone and harmonic feedback sounded lush and smooth, the owner is one fortunate man,i`m sure he will appreciate the outcome of your input, such things must never become just a collectable artefact and be used purposefully as part of the expression of music,
(that was the essence of leo fenders talent for invention) you do him proud .
Another great vid Brad! This is the best channel for amp hobbyists on YT, it fills in the gaps that are left when you’re only reading about this stuff and trying to learn. It really helps me to see how it’s wired and modded, along with reading about how it works and how it’s done. Please keep more like these coming and congrats on the new sponsor!!
A thing of beauty. I dig it. The Bassman was one of those amps that begged to be modded.
Here's my Blackface Bassman Mod video: th-cam.com/video/Oet23V3_6Nk/w-d-xo.html
LOVE this. If I ever reclaim my vintage Bassman again, I am sending to you, brother. That mod is off the hook.
That thing sounds awesome.
Seriously, a different amp that melts faces.
Very very nice!
I did it! It works!! And I learned a couple of things !!
Win, Win, Win. Thank you Doug.
One of my favorite videos of yours to date! I love seeing stuff like this.
GAWDDDDD, that one silver knob is a full blown assault on my OCDness... LOL :)
If you are explaining replacing capacitors for a second time, would that be a recap recap ?
When you wrote the tag “AB” and put it before the “Normal”, all I could think of is Young Frankenstein when the Doc (Gene Wilder) asked where the brain 🧠 came from and all Igor (Marty Feldman) could say was “Abby Somebody”, “ABy Normal”... Love this channel!
:D
Nice job. I would have appreciated you dialing the gain down on the demo to clean, to see if you can still get some of that old blackface religion out of it even after the mods. I've got a silver face Bassman just sitting around, you see...
Now give him a Sedagive !!!!
How much does a modification like this cost?And is their someone that does it for a reasonable price in L.A.??
@jacktheripped Wow, what knockers, Oh, thank you doctor...
That's an enviable amount of feedback induced sustain, these vids on amp mods are supreme.
Brad, I love your channel and look forward to your posts everyday. I grew up as an electrician and then an electronics technician before getting my EE degree, so I appreciate your hands-on approach to showing how to do amp mods. What I would really like to see, in addition to what you usually share, is the theory behind the design mods you make. It cannot be as simple as it appears; when looking at your videos, you must really know what you are doing. Uncle Doug tries to explain the theory behind his repairs, but he usually works on antique amps which are hard to compare to even 1970's - today's vintage tube amps.
Not the first time it ever happened, but its fun watching the science of electronics merge with the art of music. A great guitar amp is born! No complaints here!
the feedback thing at the end was great.
I will look at your sponsor for a new strap... instead of the local branch of the national chain. Always prefer to support small business first👍
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I watched the Guitar Straps series on this channel and IMMEDIATELY got in touch with Native Sons to get a new strap. I even ordered the "hemp backing upgrade". Best strap I have ever seen.
Great results ! Most Bassman mods on TH-cam are a clean setup, but your Bassman has a real Marshall character. Your guitar work is not too shabby either - a pleasure to hear you demo the outcome. First I've seen online - fantastic work, and thank you for such detailed play by play.
Amazing video under the board through your inspection mirror! That just doesn’t happen in ANY other TH-cam. Your enthusiasm for our education is great and that’s what keeps us coming back for more. Okay, the (very necessary) guitar demos are nice too. What got me here (you were linked), was a show on making practice amps from old radios. It would be fun to see your take on a scratch-built practice amp.
I didn't know Native Sons Goods did camera straps! Thanks to them for sponsoring!
Camera and bags for the ladies. Plus their bag straps double as banjo straps. This pleases Burt Reynolds immensely.
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Norm is the best.
One of my favorite videos so far!
Aw, thanks for saying that, man. I never know how I did until I hear feedback. I'm usually my own worst critic, seeing all the things I should have said or showed differently, etc.
Holy cow the shred at the end of this one is intense. :D
I would have loved to hear an A/B comparison of the mid toggle switch settings, and a demo of the presence knob.
Yeah, thank you Brad! Got the excat same model AC568 (export model though). Changed all of the power amp to AA864 specs. That helped the amp a lot! Will try the mid mod soon.
Nice video and mod project. Thanks for the lesson. Your experience showed in this project.
I learned long ago from my grandfather "waste not want not!!" cheers brad ;-p
That sounded amazing!! Nice work!
Its a different creature now thats for sure. Great video Brad I enjoyed it.
Thanks, man. Good to see you.
Brad, I've been thinking about this amps sound for a few weeks.... it is really so good. Now I've got my feelers out for a Bassman.. . Haha which I can't even believe I'm saying. Nice work, as always. :)
Wow, that channel doesn't sound like a Fender any more!
Killer feedback.... the best part!
Taking a trip to southern Illinois in a few weeks to pick up two bassman heads (68-69, and a 1970) for $300 a piece from a buddy of mine! I think I'll follow your mods on one. Sounds killer, Brad!!
Great job. Sounds awesome!
Hey Just watched this video. Nice work on the amp. I have a 1975 Bassman 50 head I had modified about 15 years ago. These are great sounding. versatile amps especially when modified!
Great job Brad! That thing is a beast now, crazy sustain. Nice PRS by the way!
Great guitar amp a little on the big size (watts)..I modified my 67, changed input resistors on normal #2 removed negative feedback loop.(only there to clean up signal for bass) changed cap to brighten up channel..use a 2 12 bandmaster cab with vintage 30's.. very aggressive.. love it
Congratulations! You just made a Marshall!
Excellent rebuild of the amp and great playing of the guitar.
very awesome work ! sounds fantastic !
Thanks brother, well done, I appreciate the effort!
Thanks, Steven. Appreciate that.
I have that same amp, built 12 weeks after the one in your video. That one was wired by Technician #35 in the 30th week of 1968, based on the ink stamp code near the transformer inside the chassis. I bought mine in a pawn shop for $100 in 1988. Finally re-capped it about 2 years ago.
BTW that circuit is the short-lived hybrid fixed/cathode bias circuit.
Awesome, video. My favorite TH-cam channel for tube amp. Repair / all things guitar!
Thanks for watching, James.
Ah ha !!! I see ypu have employed the knob on tuner tip from a past vid of yours. I have not forgotten. Im still waiting on the right sey of numbs to put on a guitar of mine. One day ill run into just the right set. Really cool brad. Amp looked good good and sounded great. Have a good one !!!
This is the second time I've watched this video (well I can't really watch, more like listen to it while doing dishes and house work) but after hearing what the Bassman sounds like after the mods makes me want to send you my 69 Bassman head to pimp out for more versatility during live use applications.
Thanks again Brad !
I guess this is kind of what dumble did all those years ago to a fender but it's cheaper
Sounds Beautiful!!!
Great playing! 👍
Amp sounds awesome!
I like the play by play of the mods , very nice Brad
Thanks, man.
From what I read as the amp got a little messier sometimes oscillation would happen and the .02 caps off the power tube were to make sure oscillation would happen. It's always suggested to remove those. I owned a presence control solid state rectifier blonde bass man also an aa764 or 864 an aa165 and an ab165. I had a collection of 30 vintage fenders once I got into building amps and heroin I sold all of them. The last one a 68 deluxe reverb went to Robert kealey. Anyways love your videos. Since getting off heroin 5 years is ago I work out a my house building germanium fuzz mostly. Some local amp builds and repaits. Mostly just a niche of germanium fuzz. Again man I love your videos.
I hope you kicked it.
Excellent video and mod. Sounds incredible.
Wow , a fender bassman. I used to have one back in 1974; used to put my keyboard through it. 😀
I've restored a few of this model with the 150ohm 7w cathode resistors. It was likely done to make replacement of tubes a bit more user friendly. I've always removed it and replaced with a 1ohm 1w so bias can be easily measured across it. I incorporate a pentode triode switch in place of the ground switch which gives a low hi power mode. The extra triode is very useful for a cathode follower to feed the phase splitter. I just picked up a Bass man 10 in excellent condition which I'm about to rebuild for my own evil doings...
Great sounding amp! Good job!
That is some fine guitar work at the end.
Making me feel nostalgic... Pretty sure I grew up with the same rainbow coffee mug back in the 80s.
Sounds killer 🤙
Excellent mod, I have a bassman modes in a similar fashion. I soul have liked to have heard it in its stock configuration as well. Keep up the good work thank u.
Fascinating to watch. I could smell the solder smoke.
I thought that was just me !!!
Sounds great! I don't know of many bass player who use these old Bassman amps so guitar players may as well get some good use out of them!
that thing turned out bad ass man!!!
well done! it sounds great!
I wouldn't have given it back lol! Sounds sweet. Ground one end of the shielded input feed was a useful pearl for me. I like that you were minimally invasive for future users that may want to restore to original. And if it ain't broke don't fix approach.
Bassman clean channel + JCM800 king of perfect amp !
Love the channel wish i had that amp i love the sound of em
modded Fenders done correctly kick arse. Jose (Van Halen) did my Twin. Love Bassman as well.
Wow man.. So damn amazing sounding!
Wow!!! Does that sound great!!!!
The Master Volume never exceeded 2.5.
Good job.
Thoroughly amazing (as always). Waiting for you to take a mild amplifier and mod it into Peavy 5150 territory. Come on, you can do it...
The Bassman is a great amp, paid $35.00 for one in 1982, still works and sounds great, might add the extra gain stage for optional different sound, in one way it might be considered a collectors amp however there are a million of them out there. I would still shy away from drilling.
Great job as usual Brad. Love the salty comments from the neurotic 'vintage correct' types.
The amp owner could have sold it to the vintage correct snobs for about a bazillion bucks due to all the original parts inside. Not a bad investment in that respect. ;) :D
Man that PRS was nice! The Bassman ain’t too shabby either! I’ll be yer friend, Brad!
YESSSSSS!
AWESOME VIDEO!
Oh contrar, my dear little leagers. Back in the day, I had a BASSMAN and most certainly played BASS thru it, as was customary. FENDER did offer a JBL 2X15 bottom one may aquire around '69/'70. I bought one, and used to kick some major ass for many years with it for some time. The 15's were the best thing that Fender did to upgrade it. Had a '70 Persicion to make it all good too. Great setup no matter what anyone says. Love to have it all today.
New to your channel... want to learn about amp repair. Nice playing man! Sounded Great!
Vid is just starting, but,,,i remember a jam house in the early '80s managed by the bass player. BassMan rig with the angled baffle '4x10 cab for guitar players and a GMT rig for him. I think this is what Santana used at Woostock. Any way, He complained that the guitar playres were hurting the 4 10s. Oh well. One cat had an MXR Distortion + with a Gibson LS6 (not the Chevy close by) and sounded killer. That was stock!! This turned out killer!!! Sustain forever!!
This is an awesome mod job. I love the tight dirt and the harmonic feedback is supreme. I don't know if it's the way it was recorded but I wonder if it would be possible to get a bigger, thicker sound if possible.
You can also use coax cable as shielded wire. While you can probably find cheap RG6, it's pretty bulky and cumbersome to work with, but if you find lengths of smaller stuff like RG174, its great for use inside amplifiers.
OH this is rich @The Guitologist, you really brought out the pure of mind, body and soul on this one. The "discussion" in the jchavins "troll me area" is some of the best on your channel ever. I love it when you pin these types of comments!! I am just starting to learn guitar a 55 years old so will never be a purist anyway. I spent my career as and Automotive Machinist building engines and I personally loved it when someone would see one of my custom Snap-On tools that was modified to fit my needs in the shop. I would hear "OMG you have ruined your Snap-On kiniptakator wrench by cutting the side off and bending the end like that" ..... my reply was usually "NO it was useless as a kiniptakator wrench, I don't work on kiniptakators but it is a really good quality Konkulator valve remover now that it is bent and cut." ROCK ON Brad "The Guitoligist"
Nice, I knew a kid who used to play hardcore punk with a bassman but his tone basically sounded like ripping paper. Wish he could have had some mods like what you did, would have helped him a whole lot.
An old friend bought a silver face grandmaster around 73 and had it modded then. I walked into the music shop to buy strings and there he was with his l.p. playing the solo to hotel California with a smile on his face. I said 73 but that can't be right. Obviously it was shortly after hotel California came out. The amp was sustaining into a pleasant feedback. Back then you could buy a used l.p. for 350 bucks
Sounds Great!!!!!
Use an on-on-on toggle in place of the slider bright switch to give the amp ABY capability. I doubt the bright slider would be used very much, at the very least the bright switch with the mod to the tone stack in the second channel might be redundant (bright + added gain stage or bright bypassed with gain stage + tone stack mod). Certainly an idea for the future to think about. I really like the circuit mods you installed on this monster of an amp. Great Job Brad. I love your channel man being a tinkerer myself, I've learned a ton of great stuff from you and for that I am eternally grateful and greatly appreciate your efforts.
Brad, as long as those mods that your doing keep pissing people off, well man you have got me for a friend for sure. I have the same year bassman and I think the same type of circuit, the only thing is my tech guy mounted the master volume on the back of the amp, which now I think I like it on the front the same way you have done to this amp. My amp takes pedals really well, so yeah in all I really like these mods, good job man.
Amazing amp! The joy of feed back!
I have this garbage line 6/bogner spider valve amp( the first one generation they made) that I've always wondered if it could be converted to just a regular tube amp by bypassing all the digital crap. It's got 4 el34 and 2 ax7 so it probably could be a half decent amp if it had the line 6 excommunicated out of it.
Great channel.
That feedback was on 2.5 on the Master Volume! Above 3 and the ceiling literally becomes a baffle board and the wife and police would come shoot me down like a dog in the street.
Those spider valve amps weren't that bad... Rather than trying to hack the pcb apart, just find a nice clean tone on it (or just use the fx loop if there is one, I don't remember) and hook some nice pedals through it. Those amps are really easy to make sound bad, but with some careful knob twiddling they can sound great on their own too, and with the wide world of boutique pedals (or diy pedals like from BYOC) you absolutely can make them sound fantastic.
I've been wanting a Bassman for a long time. RJ Ronquillo plays most of his videos through a Bassman head, and makes it sound great with a variety of guitars, through a variety of speaker cabinets. Since I'm getting older, the weight issue has become more weighty, and heads seem more practical now. I'd like to have a VOX head too, instead of lugging around a AC-15 (heavy) or AC-30 (heavier). There were several circuits used in the Bassman amps through the years, with earlier blonde models valued the highest. I'm appreciative that the Ampologist...I mean Guitologist, has done a video on this excellent vintage amp head, for all of us ampaholics and guitaholics - thanks!. A Traynor head can supply wonderful tone too, and not as expensive - one of those is on my "to get" list too...
(please grow your facial hair back dude - it makes you more "techie" looking)
Bassman heads aren't too heavy. Good choice if you don't like lugging heavy stuff, but need the volume onstage.
The 1968 Fender Pro Reverb AB668 circuit uses the same 7 watt power resistors and ceramic caps off the 6L6GC's. I removed all of them on my Pro and it slightly increased both the mids and treble.
Glad to see you kept the 100k plate resistors on the preamp stages instead of the nasty 220k or higher to get more gain, which in most cases makes things too fizzy and nasty. Friends don’t let friends use 220k plate resistors!
100k is usually my standard anyway. Unless I just can't get an amp to do what I want it to otherwise.
Unless it's a 6G3 Brown Deluxe ,right?
Another way to get some more sweet gain at a pre amp stage (or two), is to swap out a 22 nan by pass cap for a 470 nan plastic.
Brad's already using a 680nf on the input bypass cap. Anything smaller sounds more like a bright cap in that position. I've experimented with so many values in the classic 5F6A(values that left the factory) to JCM800 circuit, finding that both Fender and Marshall got it right the first time.
The most effective gain increase that doesn't change the overall tone has got to be changing the 1 Meg grid reference resistor to a 2.2 Meg. It's similar to adding a larger value bypass cap on the 3rd stage in a JCM800.
I've discovered that personally the .68uf bypass cap on V1 is the magic number. Anything higher and it fattens up too much usually to get those palm muted power chords and not have them muddy up. A .5uf is passable too. I'll also use that value sometimes. A 2.2M grid leak will definitely slam a stage with signal. I do that sometimes too, if I think it's necessary. Done it a time or two in past vids, I think.
COOL TONE MAN, face for radio too! lol
Hi Brad, for 07:11 no control....leave that switch in and alter it to a triode pentode output tube mode switch.
Half power output , and SMOOOOOTH , gread idea.
Maybe in the next one.
Another great vid !!! I would like to see Brad install some Relay's for Real Remote Channel Switching !! I do a 3 channel mod on Marshall 2205 , without drilling holes. It does use the Reverb tube so no reverb. But most shredders use digital reverb anyway.
thats a killer clean channel Adding the gain takes that amp over the top tone chasers love it collectors dont ...im a tone chaser should sound killer with pedals my friend n good job.
The "AB" Brad added to NORMAL makes me think of Young Frankenstein and Marty Feldman choosing the abnormal brain, thinking it was Abbie Normal's brain. Cool mod. Got some good tube distortion out of that ol' thing.
Speaking of Bassman heads,How about the model with the 220k resistors connected between the P.I. plates and power tube plates.I always cut them out. I once saw a Plush Bassman style circuit.They even copied that.You're right. It's already too loud.I can't help it.I'm always trying to squeeze more out of it. On the gig ,I used to use the Black Deluxe Reverb with the J.B.L..Now I use the Deluxe with the low wattage stock Oxford speaker.Love your love of gear.Keep it up.
JBL are great for max clean headroom. I prefer the Oxfords or similar for cone breakup.
Complaints complaints. WAH! You Done Matthew Stecker Proud! Love that feedback.
I have 3 vintage music man ampsfrom the 70's. Blonde. two 1 12's and one 2 10. I would more than happy to give you one of the 1 12's for making the other 2 work properly and pay for the parts that you may not have laying around.
I love Bassmans for guitar don’t give a stuff about bass it’s just noise to me. Brad love your work man!
There's something relaxing about watching a pro with a gnarly old soldering iron going to town.