[AlbinoBlacMan]

I'm currently getting a scratchy noise in the right channel of my project sunrise amp. It only starts to appear after about 20 minutes of listening. Once it's there than it doesn't go away, even if I unplug the amp from the DAC. Any suggestions as to what it would be? I'm going to guess that my tube is going but I thought I'd ask before I buy a new tube.

 

[AlbinoBlacMan]

Anyone have ideas? Would another possibility be that I'm picking interference from another source since the amp is so open?