Constant Hum from a Tube Amp

[VergDan]

Hi guys, I have a Orange Rocker 15 Terror. And there's a constant hum to it. My Jim Root Terror is dead silent using the same setup.

I noticed the hum when I stopped playing. It remains unchanged through both clean and dirty channel, which is quite odd as hum should be worse when switched to the dirty channel.

I have pedals in front of it, so I disconnected everything from the amp, and the hum dies down quite a lot, but still audible. When I connect just an empty cable to it, the hum grows back to the same level as before.

The hum is quite noticable in 15w mode, and not so noticable when switched to 1w or 0.5w mode, but it's still there.

Could this be from a bad power tube? That's what really worries me.

[northernguitarguy]

A bad power tube is the best likely outcome. Tube replacement is a cheap fix, and one you can do yourself. Plus, I personally would never have an amp without a backup tube set. You're gonna need them some day.

Grab new tubes and pop them in there. The only ones that need to be 'matched' are the power tubes. Plug and play.

[Les Paul Lover]

If it affects both channels, it's most likely the power valves. One of them probably is microphonic.