Marshall AVT100 combo buzz/humm

[brownsound79]

Hey guys.. my amps buzz/humm in OD channel.. it goes away when guitar volume turn down.. it only starts to hum/buzz again when i'm turn up my guitar volume..

please note: guitar got nothing to do..(tried diff axe..)

the clean channel was fine..

[PRNDL]

Preamp tubes are usually the first thing to check, although it could be many things.