AA vs AB 763
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Fender
AA vs AB 763
Re: slow down everybody...
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Posted by Andy Ruhl on June 19, 1997 at 10:00:33:
In Reply to: slow down everybody... posted by mark n on June 19, 1997 at
08:31:11:
: : :
: : : :
: : : : : I have a BF Fender Bandmaster that has the AB763 circuit.
: : : : : I understand that other models of Fender amps can also have
: : : : : an AB763 circuit.
: : : : : Does the AB763 refer to the type of components and the way
: : : : : they are assembled in the circuit?
: : : : : I have the Tube Amp Book Vol.3 (by Aspen Pittman) but it
: : : : : has only the Bandmaster AA763 circuit. What is the
: : : : : different between AA763 and AB763?
: : : : : Thanks for your response.
: : : : Hello Renaldo,
: : : : During the Fender Blackface era and on into the early Siverface
days, they used two letters followed by the date for their model numbers.
Thus a model would start with say AA763 which means "AA" for first revision
of that design, "7" meaning July and "63" meaning 1963. Thus the AB763 of
any particular model would be the next revision of the basic "763" model and
so on.
: : : : The only difference between the AA763 Bandmaster and the AB763
Bandmaster is that the AB763 model had 1.5K grid resistors added to the 6L6
output tubes. By the way, most of the AB763 models are very similar,
although an AB763 Super-Reverb will be different than an AB763 Bandmaster
for instance.
: : : : I hope this helps!
: : : : Regards,
: : : : Evan
: : : another change common to most (if not all) of the "AA763" to "AB763"
versions involved changing one of the 100K plate resisitors in the inverster
stage to 82K
: : Wait a minute, don't AA models have a .033 cap in the tone stack,
instead of a .047 on most of the AB's? I think that the Super Reverbs had a
.022. Andy
: ---->hold on!!!! let's get a few things back in perspective. first of all,
as an earlier thread eluded to, a "super" ab763 is NOT the same amp as a
"bandmaster" ab763. so first & foremost, any comparisson between aa & ab
MUST be within the same frame design or the comparisson is meaningless.
: andy, you are right, aa763 to ab763 SUPER's changed the tone stack cap
values [among other changes], but this has nothing to do with a bandmaster &
its revision from aa to ab. the orig. question was about circuit numbering [
not amp-specific, true], however the text was about renaldo's bandmaster. i
don't want to be a pain in the ass here, but we run the risk of confusing
renaldo when we start "mixing amps"
: as for the bandmaster, the aa to ab revision had more than just the 1.5k
resistors on the grids. other changes were..1.) cap value on the power
supply was 2x60uF, changed to 2x70uF, 2.) resistors added to said caps...
2x220k, 3.) 100k changed to 82k on "top" plate of the inverter, 4.)bias
resistor on inverter changed from 27k to 22k, 5.)bias resistor on "photo
side" of vibrato tube changed from 56k to 100k.
: sorry to get long winded here, but the thread seemed to be getting a bit
confused IMHO.
: ---->mark n
Mark's right. I forgot that the original amp was a bandmaster. I'm out of
town right now, so I don't have a book to go to. I know that my AA763 1x15
Pro has the .033 cap where the AB model has the .047. I think that the
Deluxes did the exact same value swap. So I figured that they all had some
kind of change here. Oops. Andy
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