I just got my ampeg svp-pro preamp in the mail today that I bought off ebay. When I went to plug it into my brothers power amp to try it out there was no sweet tubey tone just hummmmmmm. I then opened it up to find the ribbon connector was disconnected. After plugging it back in the preamp worked but there is still a nasty loud hummmm. Also the drive knob adds no overdrive just more hummm. Could it be bad tubes???? Please help me Talk Bass........
