I was looking at some Boogie schematics, and I seen a switch that lifts the inner pairs cathodes to ground. Is that all it takes for a fixed bias amp?
Don't know why more amp builders haven't followed up on the Music Man power switching , that cuts the voltage at the output transformer, simple idea.
Exactly, my view is that a key aspect of a great cranked amp tone is that the power supply sags / gets modulated by the signal; drop from four to two power tubes and the current draw will halve, and that modulation will also halve (at least, probably more so if there's an impedance mismatch too).
A (dual track) post phase splitter master volume control is almost as simple to implement, would sound better, and provide an infinitely variable range of control.
And as psychonoodler points out, VVR (rather more expensive and complex) will provide a much better result.
Do you guys think pulling the outside tubes and maybe changing speakers to two 30W speakers on each side will be ok?
Everyone seems to pull tubes, but what about changing the speakers to lower wattage as well? Anyone try this?
When you remove 2 tubes and leave the mains fuse the original value the amp is now overfused and you leave yourself wide open for a major meltdown.