I've got an amp and am experiencing a strange noise once it gets hot. It's hard to describe, but it sounds like a buzzing noise, it is only produced when the a note is played on the guitar, and it sounds like it's an octave higher (it's hard to tell exactly) than the note being played. The sound does not occur when the amp is still relatively cold. I've tried switching tubes around with no luck. Could this just be a bad pre tube?

Try tubes first. Ghost notes like you describe can also come from inadequate power supply filtering, or a bad filter cap.

 

Can you plug your amp into a different speaker? It sounds to me like you are describing "cone cry" but it is hard to tell with such a brief description. I think Weber speakers has a description of cone cry on their webpage if you want to investigate it.

TG

 

Thanks for the replies.

In fact, I did try with different speakers, same thing.

 

I had ghosting with my vibrolux..turned out the filter caps needed to be changed.

 

Got a rectifier tube in that amp? If so try replacing it.

 

...same thing happened to me, only it was a "G" note, and the noise was like a wheezing sound. turned out to be a microphonic power tube.

let your amp warm up for about twenty minutes, then tap the power tubes lightly with a pencil.

the one that makes an audible noise is defective. use a marker to draw an "X" on it, and replace both power tubes.

-dh

 

Well, I retubed it, same problem. I guess it's something more internal. It only seems to happen on the lead channel unless I just don't hear it clearly on the clean channel. I guess I'll have to look into the caps with a tech.