I just wanted to get some owner's opinions on Cafe Walter headphone amps, especially if you've had it for a while now. As soon as I got mine, I noticed an intermittent hum when I used the external power supply. When I fiddled with the PS connection on the back of the unit, the hum would disappear and reappear. It seems like the barrel (sleeve) of the PS jack is not making proper contact with the PS input on the unit. I can eventually get it to go away so it's not too big of a deal in the immediate future. I've tried the unit in different buildings and with different cables, etc. and it definitely seems to be a poor-fitting power supply. Anyone else have this problem? Also, are any of your units microphonic? I first noticed it when I unplugged my bass from the unit while the gain was up. The whole chassis became microphonic and the input jack seemed to be the source. Then when I plugged the bass back in I noticed that the cable and the pickups then became microphonic. I realize that this will happen to some degree according to how high the preamp gain is but I'm just wondering whether anyone else has experienced this phenomenon with their units. Other than that, I've been very happy with it. Couldn't ask for more gain or a clearer, more revealing sound! BTW, I got it over Christmas. Because these issues, to me, are non-critical and because my schedule for the last month and a half has been pretty crazy, I was more interested in getting opinions here before I bothered the manufacturer and/or the retailer about it.