Recently got a Laney VC30 tube amp and has a background noise, nearly like a wind sort of noise, or if you had a mic in front of a fan for want of a better explanation. It doesn't seem like guitar or ground noise. In fact it is doing it with the guitar unplugged and the amp volume on zero. I have tried turning back all the individual knobs to zero tone, reverb etc....no difference. The amp still sounds good and its not very loud, just in the background but enough to be annoying. Anyone have any ideas?