Thanks everyone for your tips. It's not the tubes. The amp plays with no issues for 33-34 minutes , then a pop then buzzing in the right channel only. I bought it preowned . Absolutely blown away by the way it pushes my Focal Kanta No 2's. It worked great for about a week. Upscale Audio tech guy is going to call me back. I just wanted to thank all of you , I don't know how to respond to individual posts.
Craig
Craig