Unfortunately I'm way out of my depth already. I can't think of anything offhand that would inject noise into both channels unless you have a noisy input preamp on some mono feed after the main inputs (I'm really guessing here, just have this vague memory of something like that) that can be mixed/panned into both output channels after the normal level controls. If you have something like that I would look there first.

Again, just a guess. It's been too many years for me to remember much, even the proper terminology.



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