Hi, I bought a BC80. When I was testing it in the store, it was noiseless, but when I brought it home, there is notable white noise. I see it wherever there is no instrument cable plugged in and that’s weird. Even more weird is that if I plug in headphones, I still hear the hiss in the muted loudspeaker. All controls on amp (volume, eq, aux in) do nothing with the hiss — it stays there, nor louder, nor quieter. Any suggestions for troubleshooting this? Is this power line related or this may be some RF interference? If I plug into my TC BG250 in same outlet and same place there is no hiss.