I was at my local GC today and saw a cool 50 watt tube Sovtec Bass head. However, it did not work quite right. When playing, I found that it caused the speakers on the cab it was hooked up to to move excessively- far too much for the relatively low volume I was playing at. Does this sound like a common, fixable problem to people who know more about amps than I do? Both power tubes were lit up, and I tried the amp on a couple of different cabinets. Thanks for taking the time to read this!