waltzingbear

its entirely possible that one channel had more leeway before breaking than the other. Hence one still working. The hum probably came from a combo of the failure (whatever it is) in the L channel from the unregulated (broken) -400 supply. I would get the LV 15V supplies working next after you get -400V regulation back. I have no idea which transistor maybe bad, but most likely one is. Once you get the supplies working correctly you should measure the voltages on both channels, that may point to the problem. The observation that it passes audio while turning on or off leads me to thi

the two things I would change are the input from single ended to balanced. simple mod, discussed elsewhere on head case, google is your friend. and add the constant current loads to the circuit. You can find this in Audio Express July, and I forget what year. there are also some grounding changes I would (did) make to get rid of some internal ground loops, yes it's our friends at Stax, they get the hard stuff right and the simple stuff wrong. Also mwl168's advice is well stated Cheers Alan

Is there a current source of earspeaker jax? I am aware of the Ampenol (WDI) parts, but are there any of the custom teflon ones available anywhere? I couldn't find them. cheapest source in US https://vacuumtubesinc.com/index.php/sockets-adapters-and-parts/5-and-6-pin-tube-sockets/a5-5285.html as a side note, contacted Richard Summer, he is moving his shop and won't be available for a (unspecified) period of time.

Thanks One of my concerns was deciding the voltage rating of the input caps, safety vs physical size. I'm used to having the SRM1 MK2 on my workstation and want to fit the new amp in as well as I can. Cheers and thanks for the info. It is indeed what I was looking for.

Greetings In the process of gathering parts and am down to psu and transformer choices. Blueman2, have you gotten your transformers or are they just ordered. I was wondering what the actual performance is (voltage with and without load) TIA Alan