This was originally a Fender Bassman 50, but it had been heavily modified. One channel had been converted to an early Bandmaster, and the other channel had been converted into a distortion channel. The phase inverter/output stage had been modified as well. Unfortunately, the amp sounded thin, lifeless, and buzzy.
The owner got a good deal on the amp, and liked the idea of the distortion channel, so he gave me free reign to tweak it.
A customer had given me a nice Dario Miniwatt EF86 a few months ago, and I had been wanting to use it for something cool, so for the clean channel I used a single 12AX7 triode to drive the EF86. The "bright" switch now increases the gain of that input triode enough to distort the EF86 and produce all those interesting pentode overtones.
The overdrive channel uses the 3 remaining 12AX7 triodes for a higher-gain marshall type preamp. The "bright" switch in that channel now switches between a smooth rhythm overdrive and a more aggressive lead distortion.
I decided to run a pair of KT66s into an 8Ω load for a JTM45 style output stage.
The chassis had previously been drilled out for a "mid" control. I used it for a classic Vox "cut" control which works like a presence control for both channels.
The modified amp sounds best cranked, so I installed a mosfet power regulator circuit which allows the owner to bring the amp anywhere from full power down to less than 1/4W with very little effect on tone.
I used the original boards, sockets, pots, and even wire where possible - so it's not the neatest build ever. But I love the tone! It's the man amp!
