This will be one of my last projects. It will solve a few of the problems I have encounted, much due to my on liking of small stuff. My Sonido hornspeakers are a suitable load for small amplifiers, even down to 1W, but I have a pair of heavier 2-way speakers that require more "juice". A pair of GU-72, Russian tetrodes are capable of delivering over 25W/channel in single end. They are easy to drive, doesn't require suicidal anode voltages and look beefy. The only drawback - the BIG anode connector on top of the tube.

Two major questions: Howw to make the electrons move inside the GU-72 and how to fix a suitable chassis?
Second question is easy; I have a pair of bigg Hammond steel chassis and a cover made of thick Corian sheets, or bricks maybe. Corian is a sort of composite stone, looking a bit like marble. The material can easily be milled, drilled, sawed, turned etc. I want the chassis to withstand the tube, and the transformers (Hammond 1627). Mains transformers are special wound from and, because I missed a few voltages when ordering the big toroid, standard transformers.
What driver to use is another question and I haven't decided yet. The schematics hint that 6SN7 can be used, but I guess "almost" anything can be used but some of my favourites are C3g and 6E5P. When looking deeper into 6E5P as driver, and this also may an idea with C3g, to use a CCS instead of anode resistor.

BUT, there's yet another thing I have to check into, using a 6S19P, a rather powerful triode as driver ...









Bartola on gyrators

Millet on CCS


<6E5P as driver/p>

C3g data