Bought this un-tested to pair with my M1A. It crackles, pops, hums, and generally is very noisy with any input. It is dead-quiet without input. Tuners give it 60hz hum Any switch push = pop (including switches on input devices) DAC pops when changing modes Computer output has a machine buzz All of these devices are very quiet, no buzz/hum/pop on other preamps. Using a different preamp with the same M1A amp and the same devices above also is very quiet, ... so the only common component is the C1. Is there a coupling or isolating component that seems like a good place to start? I hate to just jump in and re-cap and replace components without identifying the problem first. Seems like an open ground, ... but the ground path in this thing is not simple. Any thoughts or clues?