I have a problem here that I hope you guys can help with. I have a Kustom Groovebass that I put in the shop because of an unusual amount of noise that I was getting. I was playing it in rehearsal and I heard my sound break up and the volume dropped. Then it came back but there was some noise coming from it. It was an electrical noise for all I know and it seems to come from the amp. I thought it was one of my basses but changing those produced the same result. I tried different instrument and speaker cables and nothing. Even with no instruments plugged in I got the hum. Sounds similiar to 60 cycle hum but louder. So I bring it home and try a different cab and same thing. So that is in the shop. Then I try my backup head that I just got, a Behringer BX4500H and plug into my main rig(Avatar B212) and that head produces noise also. Not as loud as the Groove Bass but there is noise. A couple of weeks ago my rig was quiet but all of a sudden there is tons of noise. I do the same thing with the Behringer and bring it home and same thing I get noise. So I plug in my Yorkville XM200 into the Behringer return line bypassing the pre and the noise disappears. So I think that I got a noisy pre in the Behringer so I am returning it and getting a Hartke HA3000 for practice and backup. If this head gives me the same noise then what is the problem? Also I messed with my Avatar B212 because I put the new crossover in it a couple of weeks ago and when I removed the plate the noise stopped for a brief second then came back on. But touching and moving the plate did not duplicate that response. I have no idea what is going on but it seems that all my stuff is acting crazy now. I would appreciate some input from you guys as to what you think it is or has anyone else experienced something like this. I remember that Tombowlus said in his reviews of the Groovebass that it is susceptible to noise issues. What can I do to improve this? I have not heard back from the repair tech yet.