Dating fender power transformers
Let’s study the blackface Bandmaster AB763 and blackface Bassman AA864.
They are similar in the way that both are clean sounding with just one 12ax7 tube in the preamp stage (vibrato ch in bandmaster and normal channel in bassman).
This mod does not alter the tone significantly when amp is played clean or when only the power amp section distorts.
You’ll have to increase the volume setting to achieve a similar volume as before.
Five fundamental tricks to create the holy grail of Fender tone Here is a video demonstrating the effects of some of the mods and tricks described here.
To see embedded text comments, go to video on Youtube.
Finally we point out location of components in the physical layout diagram.
The reverb amps will start to break up around 4-5 on the volume knob while the non-reverb amps stay clean to approx 6-7.