I have been listening to my Valhalla for a little while (just got it about 3 weeks ago) and noticing that one side will be predominant. I have swapped my tubes back and forth and noticed it goes away for a couple of days and returns. Figured I would email the guys over at Schiit because they have been responsive on other fronts. Within 10 minutes of me sending my email this morning at 1000EST I had a response, they are sending me a replacement set of tubes. I cannot tell you enough how happy I am with their products and their fantastic support. Cannot wait to buy their DAC!