Hi, wasn't totally sure where to ask this, so I figured here might be good rather than starting a new thread since I am a newb to your forums (long time lurker though). I have a WA3 that I got a couple weeks ago and I am running Sennheiser HD600s on it. I probably have <20 hours of listening on it so far. The sound is amazing, even during its problem. There is an occasional hum, sometimes it hums continuously, sometimes it comes and goes, and other times it doesn't at all. It is always in the right channel, I tried swapping the driver tubes and nothing changed. It is fairly low in pitch and somewhat quiet, I don't notice it when music is playing. Usually when I touch or tap gently on the amp the hum goes away temporarily. Volume does not effect the hum. Sometimes it will come back pretty quick or stay quiet the rest of the night. Does anyone have any ideas about what is going on?