Try switching one by one each tube from one channel to the other and see if and when the noise/distortion changes channels. Then you'll know if it is a tube and which one.
Tube amp question
I have an Allied Model 333 tube amp/receiver that has been working fine for some time now. All of a sudden, it has developed a noise/distortion in the right channel which is very noticeable. Is this the sign of a bad tube or something more? I use this amp when I listen to vinyl. Any suggestions? Thanks