Strange problem with Rivera R55 amp

[jordan]

Hey all,

I'm getting a strange intermittent feedback with my Rivera R55 tube amp, which may be easily explained by someone in the know.
It's not happening all the time, but last night even when I'd turned both the guitar's volume and the volume pedal all the way down, there was a feedback-like noise coming from the amp. I got rid of it by putting the amp into standby, then turning back on. This happened a few times, and after a while the feedback disappeared.

I've heard the phrase 'microphonic valve' used in this situation before, but I'm not entirely sure what it means(!). When in use, the amp sounds fantastic, and certainly not as if the valves are dying. This problem has happened with both a strat and a wolfgang, so that also rules out the guitar/pickups I guess. The valves (2x EL34 and 5x 12AX7) are less that a year old.

So, does anyone have any ideas as to what could be causing it?

Cheers,
Jordan

[hunter]

power up the amp and turn up the volume, then use a pen or sth and tip the tubes gently, if you get weirdo noises on one of them (pre/power) it might be overdue.

But it could also have to do with the wiring of your rig, maybe a defective cable or so could also be the reason.

I suggest, if the tube thing doesn't clarify, swap out parts item by item and see whether the issue still appears. If you have spare cables and spare guitars, that would make things easier obviously ...

that's all that would come to my mind.

After this I'd go to the dealer, reproduce the issue there and have him fix it ...

[HTH AMPS]

it's an odds on bet to be the first-stage preamp valve (ECC83)

 :twisted: