Dating blackface amps
The Bassman has a slightly bigger output transformer resulting in a firmer tone and more attack.
A smaller output transformer will introduce sag and compression in the power amp section.
This makes it possible to adapt to small and big stages and gigs just by configuring the speakers.
Most of the maintenance and mod tips below will make the amp break up earlier, reaching the sweet spot at a lower volume.
The reason is that 12AX7 tube has a voltage gain factor = 100, while 12AT7 = 60 and 12AY7 = 45.
Pull out the V1 normal channel preamp tube – More preamp gain in vibrato channel We’ll start with saying that this is a mod we personally do to all dual channel blackface, silverface and reissue amps.
Not only is there more action in the preamp section, the silverface Bandmaster Reverb also has less attack and less clean headroom in the power amp section due to the tube rectifier.
The Bandmaster Reverb head is therefore quite similar to the amps in the Pro Reverb and Vibrolux Reverb, just without the speakers.
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).The blackface Bandmaster is therefore ideal for those who look for a pure Fender clean sound without making ones ears bleed.The blackface and silverface Bandmasters are medium/big sounding amps with a flexible speaker impedance of 4 ohm, allowing anything between one and four speakers (8 ohm each) to be connected via the main and/or external speaker jack.These tubes have different frequency responses than 12AX7, particurlarly when distorting.People describe these tubes to have less harsh and buzzy distortion.