So the audio from the PC into the mixer could have been low or
perhaps a bad earth there? Just a guess..

Well the audio was certainly low.... as to being non-existant... there are already known earth loop hum problems going on, but no one has any idea how to get rid of them. It usually gets a low filter to try alleviate it. It turns out the move was to much for the power supply for the pc side mixer. Its what I






























































































consider to be a weird 17VAC x2 power supply. And it's delivering.... NOTHING... and I'm guessing the hum is just the empty load on the pc inputs.

What gets interesting in my mind anyway is a supply delivering 17VAC x2 @ 200mA. Thats weird current even if you still rectify it on board into DC, plus






























































































the device will supply something called "ghost power +54v". So my guess is that 2x17VAC out of phase helps supply the 54 if its needed but we never use it. And one of the 17s becomes the onboard DC as well. Shrug.

I thought one of my old AC modem power supplies might do the job, but alas she's some 8 volts short of the requirement, even if at way higher current.

Spec


--- SuperBBS v1.17-3 (Eval)
* Origin: (21:3/101)