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.

 

[Ascension]

Re: Constant Hum from a Tube Amp

Can be a number of things. Some amps effects loops are noisy like the PRS MT 15 can also be the type preamp tubes used some are just noisy in some amps some amps are just noisy at high gain settings. Most likely cause in my experience is pre amp tubes.

 

[SlyFoxx]

Re: Constant Hum from a Tube Amp

How old is it? Filter caps don't last forever. When they begin to fail a bit of 50 or 60 cycle AC hum is the result.

 

[devastone]

Re: Constant Hum from a Tube Amp

Has it always done this or did it just start?

 

[JMP/HBE]

Re: Constant Hum from a Tube Amp

 

[ErikH]

Re: Constant Hum from a Tube Amp

Change V1, the first pre-amp tube. That is the first place any noise will come in and will only get amplified through the rest of the gain stages. The old Marshall JCM 900 MkIII I used to own did that with some Sovtek preamp tubes. Electro-Harmonix was better but I ultimately went with JJ tubes throughout. Changing that V1 from a Sovtek to a JJ made it real quiet. Once I changed V2 and V3, it was perfect. You may have to try a few different ones out to find the one that is quietest for the amp.

 

[JMP/HBE]

Re: Constant Hum from a Tube Amp

There are 50+ reasons why an amp can hum & you get to figure out which ones.