Quote Originally Posted by duhvoodooman View Post
P.S. Just started a new amp build project. I picked up a BYOC Brit 45 head kit (Marshall JTM45 "Bluesbreaker" clone) and am modifying it to JTM50 specs--think 50W Plexi with a tube rectifier. The two circuits are very similar, with the major difference being that I'm installing EL34s instead of the KT66s in the JTM45, and am using a 50W Plexi output transformer to match up the primary's impedance with that tube type. The other major modification is the installation of a variable voltage regulator (VVR) in the power supply stage that allows you to dial down the final output while still keeping the amp "cranked" for that sweet Marshall crunch. Similar idea to using an attenuator, but by reducing the voltage supplied to the amp circuitry rather than attenuating the output with a resistive or reactive load, and thereby results in less tonal change.
In surfing around looking at amps I re-read this. Seems like similar idea to the new-ish Fender Bassbreaker 45 which reportedly also has that feature. Yes? It is also based on the Bassman circuit, but voiced a bit british. Looks pretty cool.

See vid at 1:30 for discussion of the variable output feature.

https://www.youtube.com/watch?v=A9iL2uFvfqg

http://shop.fender.com/en-US/guitar-...265000000.html