EmRR said:Well, you've got too much noise without the input transformer too, right? Swap the input transformers?
The transplants I propose can just be disconnections and wire moves, you don't have to move the whole PSU/etc.
Now that you mention it, I believe I did test this without the input transformer (simulating an instrument input).
I even went so far as to replace everything on the audio board (caps, resistors...), just in case ANYTHING was acting goofy.
We can rule out phantom power. That's not even hooked up. There are no switches of any kind in the signal path. It's as basic as I can get it.
I'll get both preamps on the bench by the end of the week. One way or another, I'll see what combination of preamp/power supply works or doesn't. Not much point in introducing the IS and PP stages until I get this licked.