Well, may first taste of tubes has been bitter so far. I recieved ny V.A.L. E10 Tube headphone amp and it has an issue. It plays fine for about 30 minutes or so then the music cuts out and I get a whine in both channels. I have removed the tube and seated it 4 times. Same thing. It sounds fine till buzz kicks in and the music stops playing. Any idea's? Sounds to my like a PSU cap. Could a bad tube cause this problem? The amp uses a tube for the input stage and I think solid state for the output.