What causes distortion on tube amps?

[trod93]

Hi to all.

I'm having distortion on both channels from my el84 tube amp lately. At first, I could only hear it on acoustic guitar, particularly, on the higher bass level. Now, it seems to be spreading. Could it be the output tubes are "dying" already. Or, could it be something else? I've experimented on changing the driver tubes (5 pairs) on the pre and power amp, as well as, the rectifier (3) but I still get the same result. I don't have spares for the el84 to test. I tested my speakers on my ss amp and it sounded fine.

Will appreciate any input.

Thanks.

[arnoldc]

I'd suspect the bias circuitry first. It might be whacked out. The other culprit could be the power supply.

Send it in for service.

[trod93]

I had it checked by mang rod 2 weeks ago, for a different reason, though. Yup, maybe I need to bring it back for a thorough check up. The Payatas Boys might drop by for a listen and this amp could be the subject for scrutiny.

Thanks.