My Vetta Combo II has a serious issue that has me pulling out my hair at this point trying to figure it out. On all my high gain patches there is a serious buzzing/hum noise that sounds like when you have a cheap guitar plugged into an amp. When I use the noise gate it cuts it out a few seconds after playing but when the gate is off it buzzes/hums super loud. I borrowed my brothers Furman power conditioner to try to see if it was a dirty power supply in my house, tried to combo at a friends house and even brought it to a studio setting to try it with no luck. I have tried several guitars including active and passive pickups. My 8 String Custom ESP even does it so I know it's not the guitar. Any suggestions or fixes?
Maybe take it to a tech and see if you have a noisy power supply or something like that. They should be able to track it down by scopeing the power supplies and doing a bit of signal tracing.