So I traded my GK2001RB for an Aguilar AG500 (dual channel) and its been nothing but problems since I've gotten it. When I got it in the mail, I had to shell out to get it fixed. The channel switch was broken among other things. Now whenever I play a note I get distortion. Its low level but definitely there. When I don't have an instrument plugged in I don't get anything. If I just fret a note, even at low volume, you'll hear it. It sounds like I have a distortion pedal put in. No amount of different basses, cables, or cabs, seems to fix this issue. No twiddling with the EQ or anything seems to fix it. When my tech fixed it the first time, he said it was a poorly designed amp (internally) that was extremely fragile and if anything broke on the amp again to just junk it as things would just keep breaking. I was also told never to push this amp as it couldn't even stand the abuse. I trust my tech a lot. He ghost builds point to point tube amps for a couple of companies and will rewire every Marshall that comes through his doors as their circuit board is flawed from the getgo. He treats everything like it was his own. Any help on isolating this issue? I contacted Aguilar and all they offered was to fix it for $90 an hour instead of helping me isolate the problem. I already knew it wasn't under warranty.