Thanks Gordon... silly question, right?... I have one of those! again, it is good knews that now you are back to business Khenegar. So, the cracking noise was coming from the preamp, extrange that only when you cut the power mains A.C. you got that odd sound. Still thinking in a posibility of a capacitor. Usually at the output, you find a device that we called voltage divisor, and use an electrolitic cap, 4.7uF with the posive lead at the preamp, and the negative lead is the output...this array will make that any DC unbalanced coming from the pre, will be kept and will not come out, just the AC, in this case the music. If you have DC coming out from the pre circuit could damage the input stage of the amplifier... some manufactures after the input resistance for impedance, use another capacitor to avoid the also DC at the terminal RCA or BALANCED input. Happy listening,
R.
