Really weird preamp question!

[nathanvacha]

Maybe this should be in Geekslutz, but we'll try it here. My issue is this: I was plugging into a preamp i haven't used in a long time, it's an art t.p.s. and i wanted to try it as i remembered it had a good amount of fairly clean gain. However, when i turned the gain up high, i got a crazy sound... Not from the speakers, but from the microphone!
It was sending signal to the microphone.

I don't remember it doing this before, and i recently shortened some a.c. cables inside my rack by installing new plugs. Could this problem be a reverse in electrical polarity if the power cable was originally using the wrong colors for conductors, or is it a broken pre?

Anyone heard of anything like this before?

[pkautzsch]

Don't think it's got to do with power polarity.
Some wiring in the signal path is wrong. Is there any chance of having the input cable plugged into the output connector (e.g. are they both TRS?)? Or that the internal wiring is wrong (maybe...a mouse inside the pre...you said you haven't used it for a longer time )? Probably just a misconnected patch cable in your patchbay? (yeah, the most stunning errors are not produced by technical stuff but by human beings - and it's been there all the time, right in front of my nose)

[nathanvacha]

Well, I plugged directly into the front panel, but come to think of it, i forget how it's connected in the patchbay... I may have carelessly normalled input to output and never thought of it again because i haven't been using it... Could that send signal out of the input?