TC-50 Distorts After Warm-Up

[tuned88]

Hi - first post on this forum. I've recently noticed that 5-6 minutes after I power up the amp, my clean channel is no longer clean. It has a nasty raspiness that's not as noticeable on channels 2 & 3. My guess is a tube or some other component is failing. Any suggestions would be much appreciated.

Thanks All

 

[bandit2013]

I would suspect the FX tube (V5). Not sure when you got your TC-50. Mine had a Mesa Chinese 12AT7 of which I found can become unstable. Most of the time I had more of a blanketed tone (TC-100) and could not get the amp to sound to match its power rating. I have both TC-100 and TC-50. Note that the FX tube is always active in the signal path regardless if you have something in the FX .loop or you have it turned off with the toggle or footswitch.

The other tube to check is the phase inverter. This in many cases can lead to clean channel distortion issues.

You can also try swapping V1 and V2 as there is an unused triode on V2.

But your description of the issue almost lends itself to the power tubes. That is how I feel the Mesa STR447 EL34 sound generally. harsh and raspy.
Sorry if this is not helping.