I believe there is a way to test a power amp by shorting or using a resistor at the input. I don't know the process, but one of the Gurus might be able to explain. Don't try it till someone posts the proper procedure !!!
Just unplug your preamp and short the two inputs, on the amp. You can also make a pair of shorted rca plugs. It wont hurt anything and you'll be able to tell if the problem is in the amp or preamp-cables.
Welcome to the problem of electronic interference. Thats why we shield most of our cables. If you don't have any source of ground the circuit becomes an antenna. If you pull the ground off of your input when playing a signal it will put the amp into oscillation. Not pleasant.
Yep, amp has no ground yet. Drilled holes to do star (?) ground scheme and has not gone there yet. Strangely month or so no hum and absolute silence was in speakers.
Just to be clear - unplugging is not the same as shorting. I wasn't sure you got that. All MyRefs I have made make noise/hum with nothing attached to the input.
I am just referring to the two rca-input pins (Molex). If you connect the ground (spade) on the board it will introduce noise. Some people use the shorted rca plugs to plug any unused source inputs to silence any unused input circuits.
Here is the basic idea. Just some sort of loop/connection between signal/hot post and ground/shell. Can be a wire or just a big blob of solder. Some use a resistor for special applications, but I don't think it is necessary for what you are trying to do.
I plugged intecronnect and shorted other side with wire.
Left channel: down from approx 30 to 5, 4 or 1 mv and fluctuating between
Right channel was weird- down from 45 to negative side (approx -16) and then up to +25... fluctuated.
