Fender Deluxe AA / AB 763: Good amp?

Wharfcreek

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So somewhere in this multitude of threads and posts there lies a story about a guy who had a Fender Super Champ X2 that shot craps on him. While a good many said 'just throw it away and start over!!', I suggested that he 'gut' the thing and maybe try building something out of it. A few posts came back saying "... can't be done...too crowded a platform!" or something similar. But, I think maybe these guys were thinking that 'building something' would involve still retaining the original circuit board, controls, etc. My thought was to literally 'gut' the amp, and use just the output transformer and power transformer, and literally build a new amp.

As it worked out, I decided to rise to this challenge, and purchased a perfectly good Super Champ X2, and I DID 'gut' it! I even pulled the face-sticker off of it! And, I've used the original 3 holes where the former tube sockets were to install new octal and a nine pin socket, and I've drilled a hole for a 4th socket, another 9-pin. I then ran the heater lines to all 4 sockets and fired the amp up with tubes installed so as to determine if the added current draw from the 4th tube heater would be too much for the power transformer. I'm glad to report that after several hours of just 'on' time, the PT has remained essentially as cool as the proverbial cucumber!! So, with that hurdle now over, it became time to find a suitable 'build' schematic.

I've wrestled with this, as there are really a lot of options here. A push-pull 6V6 amp can be 'driven' with a 7-pin 6AV6 tube, which is essentially 1/2 a 12AX7. So, virtually any of the old Fender designs that use 1/2 the 12AX7 as the phase inverter can be built using 'just' the 6AV6 to replace it. This then leaves the other 12AX7 for first stage gain and then the tone controls.

OR,

I got to looking at this AA763 / AB763 Deluxe circuit, and got to thinking: Maybe IT'S the way to go? Honestly, I've never owned one of those amps. And, if I were to build this circuit, it would be WITHOUT the Vibrato section. I never used that anyway! But, I guess this post is to just Queary the group here and see what you all think about this amp circuit vs others. As it worked out, the Super Champ X2 power transformer DOES have a winding that can be used to source a 'negative' voltage supply..... so I can go with a 'fixed' bias build. I was also 'originally' thinking about just building the Super Champ as a point-to-point unit, but without all the digital mess. That could be done as per above using the 6AV6 for a phase inverter and the one 12AX7 for just a treble/bass tone stack (or maybe add a mid range, I dunno). But, in looking at this later Deluxe AA / AB schematic, and with the different phase inverter design, I though maybe it might have some advantages. So......... help me out here!! What do you think???.............

Thanks, Tom D.
 

schmee

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So somewhere in this multitude of threads and posts there lies a story about a guy who had a Fender Super Champ X2 that shot craps on him. While a good many said 'just throw it away and start over!!', I suggested that he 'gut' the thing and maybe try building something out of it. A few posts came back saying "... can't be done...too crowded a platform!" or something similar. But, I think maybe these guys were thinking that 'building something' would involve still retaining the original circuit board, controls, etc. My thought was to literally 'gut' the amp, and use just the output transformer and power transformer, and literally build a new amp.

As it worked out, I decided to rise to this challenge, and purchased a perfectly good Super Champ X2, and I DID 'gut' it! I even pulled the face-sticker off of it! And, I've used the original 3 holes where the former tube sockets were to install new octal and a nine pin socket, and I've drilled a hole for a 4th socket, another 9-pin. I then ran the heater lines to all 4 sockets and fired the amp up with tubes installed so as to determine if the added current draw from the 4th tube heater would be too much for the power transformer. I'm glad to report that after several hours of just 'on' time, the PT has remained essentially as cool as the proverbial cucumber!! So, with that hurdle now over, it became time to find a suitable 'build' schematic.

I've wrestled with this, as there are really a lot of options here. A push-pull 6V6 amp can be 'driven' with a 7-pin 6AV6 tube, which is essentially 1/2 a 12AX7. So, virtually any of the old Fender designs that use 1/2 the 12AX7 as the phase inverter can be built using 'just' the 6AV6 to replace it. This then leaves the other 12AX7 for first stage gain and then the tone controls.

OR,

I got to looking at this AA763 / AB763 Deluxe circuit, and got to thinking: Maybe IT'S the way to go? Honestly, I've never owned one of those amps. And, if I were to build this circuit, it would be WITHOUT the Vibrato section. I never used that anyway! But, I guess this post is to just Queary the group here and see what you all think about this amp circuit vs others. As it worked out, the Super Champ X2 power transformer DOES have a winding that can be used to source a 'negative' voltage supply..... so I can go with a 'fixed' bias build. I was also 'originally' thinking about just building the Super Champ as a point-to-point unit, but without all the digital mess. That could be done as per above using the 6AV6 for a phase inverter and the one 12AX7 for just a treble/bass tone stack (or maybe add a mid range, I dunno). But, in looking at this later Deluxe AA / AB schematic, and with the different phase inverter design, I though maybe it might have some advantages. So......... help me out here!! What do you think???.............

Thanks, Tom D.
If you are talking about the non reverb BF Deluxe, its a superb amp and my main gigging amp at this point. Sold the BFDR a couple years ago , which I had as well.
I'm not sure if the vibrato circuits add something to the tone of the amp or not. (when off) But I have experimented with BFDR and other Fender circuits, eliminating the reverb and trem in the past. For some reason I did not find I liked it as well as the stock circuit. (with both off) But who knows, it's not like I took a vintage amp and modded it, so hard to compare really with all the different components.

To me you gotta have a rectifier tube for the full experience though.
 

Wharfcreek

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Yea, I know I'll be on the 'short' end by not having a rectifier tube. BUT....... I swing both ways on this issue. I've had some guitar amps where the rectifier tube was a definite part of the amp's mojo. Yet, in others, replacing it with a solid-state plug-in made a world of difference! Case in point would be my old Super Reverb. That amp was definitely improved by that change. I'm not sure how the power supply filter caps like it......but.... hey..... they've been replaced once already, so if they ever need it again, I have a spare set for the job.

I don't know if you've ever played one of these Super Champ X2 amps, but I was really surprised by it. So much so that after I bought the first one to 'gut' and do this rebuild project, I actually went out and purchased a 2nd, and then an XD version....which then led to a Champ 12. Honestly, I'd never played any of these amps in all my years of doing this. I think that when Fender left the silver face era behind, I kinda dropped out of the guitar amp world. By the time I got back 'in' to it, most everything had gone solid state..... and that had no real appeal to me. So, I started looking for and buying old 'vintage' amps, which took me through the last 30 years or so. But, somewhere when the tube world was being left behind and the 'digital' world was coming into it's own, Fender came up with these 'hybrid' amps, with 'tube' output sections, but solid state / digital front ends. And, frankly, they don't sound too bad! I mean I play with a digital delay pedal in front of my old Tweed Deluxe or Champ, so having this whole 'digital' front end really isn't all that much different. Granted, no tube gain stage, and certainly no tube rectifier..... but...these little amps do have some punch, and I like that!

Anyway.... the power transformer has no center tap on the HV leads, so even if I wanted to add a tube rectifier, I couldn't really do it. I suppose I could change out the PT, but then I'm rather defeating the purpose of 're-purposing' the whole Super Champ platform into a truly 'all tube' amp (sans rectifier). But, I'm liking the 'Black Face' Deluxe idea, and thinking that with two 9-pin tubes and the two 6V6 output tubes, I could maybe do a version of the AA / AB 763 that might be respectable. I guess that's the question: Is it worth a try!
 

Wharfcreek

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Actually, it's funny you should mention that! I actually DID build a 5F6A 'clone' about 25 years ago. I had an old Super Reverb output transformer and decided to do the 5F6A around that OT. I built the amp on an old Fender Chassis of some unknown origin.....but I think it might have been an old Bandmaster chassis. At any rate, that amp went through a household move with me back about 23 years ago and has been on a shelf for nearly that entire time.....until about 2 weeks ago when I got it down, dusted it off, plugged it up on my variac, and brought it back to life. After about 30 minutes of play time I realized just what a nice amp it actually was, and decided it needed some further attention, including a good enclosure. So, as of about 3 days ago it got dropped off at a local cabinet builder's shop where he's going to do a complete 'custom' cabinet around it...... 'head' type that is! I probably won't see it for a few more weeks, but I just got off a 'text' thread with him to order a matching speaker cabinet to be built as well. An 'enclosure' that will be provided with 3 baffle boards, a 1X12, 2X10, and a 1X15. Not sure how this will all play out with a 2 ohm output transformer, but I also ordered a 4 ohm 'bassman' replacement output transformer from AES that I may just drop in to that amp chassis just so I can use more 'appropriate' speakers. But..... all this said, I'm not sure that the 5F6A really IS a 'be done with it' type amp! Granted, it's a GREAT amp, but I tend to think that it's really just another 'tool' in the shop! And, I'm kinda 'growing out' of 'BIG' amps! Even my home audio system has gone from big speakers and big amps to 'smaller' speakers and 'flea watt' amps! But, we'll see how this all plays out! I think the Super Champ X2 rebuild is going to be something like a Princeton Reverb only without the Reverb, tremolo, and with 3 gain stages. That seems to make the most sense to me at this point............
 

TwoBear

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That little Princeton circuit that was around for one or two years the black face one with the white knobs is a good sounding little amp.

I used to play with a singer songwriter showcasing his songs and we both played through Princeton’s-he played a telecaster through his black faced white knob Princeton and I played a Strat, and other guitars through my silver face Princeton, Which had a changed out baffle and a 12 inch EV SRO.

I used to get compliments on my tone all the time in other projects, but when I played with that guy I really liked his sound better than mine!

I think maybe that model was a transition from the brown period-holding over to just a tone control.

I’m a big fan of those amplifiers with just a tone control or a bypass of the tone stack mod. I’m not sure about the negative feedback on that, and whether they had gone to a fixed bias by then, But that little amp had a nice growl to it.
 

Wharfcreek

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I'm going to try to attach the circuit I've been looking at to build to this post. As you'll see, it's a 'fixed bias' design, and appears to be pretty close to a typical black/silver face Princeton from the '60s / '70s. I think any feedback can be varied to taste, and honestly I find that sometimes a tweak to that value is as much a function of speaker being used vs the design of the amp. Hence a 'variable' feedback is often the way to go if possible. I'm just not sure about adding the third gain stage, or how the PI section will affect the amp, vs that floating paraphase used in the 'early' Princetons alone with only a 2-stage pre-amp section. I guess this is kind of what defines the 'old' Princeton circuit from the new one. Anyway, posting the schematic, and your comments are appreciated. BTW, I probably owe a 'credit' to the person from whom this circuit came, but sadly I can't find that info anymore. So, my apologies to that individual, but credit goes to that person for the circuit attached. Tom D.
 

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dannyh

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That little Princeton circuit that was around for one or two years the black face one with the white knobs is a good sounding little amp.

I used to play with a singer songwriter showcasing his songs and we both played through Princeton’s-he played a telecaster through his black faced white knob Princeton and I played a Strat, and other guitars through my silver face Princeton, Which had a changed out baffle and a 12 inch EV SRO.

I used to get compliments on my tone all the time in other projects, but when I played with that guy I really liked his sound better than mine!

I think maybe that model was a transition from the brown period-holding over to just a tone control.

I’m a big fan of those amplifiers with just a tone control or a bypass of the tone stack mod. I’m not sure about the negative feedback on that, and whether they had gone to a fixed bias by then, But that little amp had a nice growl to it.
The Tuxedo Princetons were the 6G2 brownface circuit. The was a run of them that got out of the factory with a 250K volume pot instead of the drawing 1M pot (a pretty large run of them actually), but otherwise I think they were pretty identical to the Brown Princetons.
 

schmee

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Yea, I know I'll be on the 'short' end by not having a rectifier tube. BUT....... I swing both ways on this issue. I've had some guitar amps where the rectifier tube was a definite part of the amp's mojo. Yet, in others, replacing it with a solid-state plug-in made a world of difference! Case in point would be my old Super Reverb. That amp was definitely improved by that change. I'm not sure how the power supply filter caps like it......but.... hey..... they've been replaced once already, so if they ever need it again, I have a spare set for the job.
I don't know if you've ever played one of these Super Champ X2 amps, but I was really surprised by it. So much so that after I bought the first one to 'gut' and do this rebuild project, I actually went out and purchased a 2nd, and then an XD version....which then led to a Champ 12. Honestly, I'd never played any of these amps in all my years of doing this. I think that when Fender left the silver face era behind, I kinda dropped out of the guitar amp world. By the time I got back 'in' to it, most everything had gone solid state..... and that had no real appeal to me. So, I started looking for and buying old 'vintage' amps, which took me through the last 30 years or so. But, somewhere when the tube world was being left behind and the 'digital' world was coming into it's own, Fender came up with these 'hybrid' amps, with 'tube' output sections, but solid state / digital front ends. And, frankly, they don't sound too bad! I mean I play with a digital delay pedal in front of my old Tweed Deluxe or Champ, so having this whole 'digital' front end really isn't all that much different. Granted, no tube gain stage, and certainly no tube rectifier..... but...these little amps do have some punch, and I like that!

Anyway.... the power transformer has no center tap on the HV leads, so even if I wanted to add a tube rectifier, I couldn't really do it. I suppose I could change out the PT, but then I'm rather defeating the purpose of 're-purposing' the whole Super Champ platform into a truly 'all tube' amp (sans rectifier). But, I'm liking the 'Black Face' Deluxe idea, and thinking that with two 9-pin tubes and the two 6V6 output tubes, I could maybe do a version of the AA / AB 763 that might be respectable. I guess that's the question: Is it worth a try!
Yeah, if you need a limited amp to sound cleaner at higher volume the SS rectifier an make a difference in low end flub. I usually get there better with a robust speaker instead, but it's an option.
Yes, I have had all those amps. Sold the Champ 12 fairly recently. I liked it, but a bit noisy and the on line mods didn't really fix it entirely. I built a 6L6 VibroChamp with bigger OT instead and it's far better.
The XD and X2 are decent sounding amps, But throw away amps really due to the digital boards.
 




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