Hi, I have two B100r's that I love dearly. One is dead silent no matter what and the second has a very low level 120cycle (I believe) hum present all the time along with *slightly* diminished output. The low level hum is present as soon as the amp is switched on. None of the controls make any difference. Still hums the same if all full clockwise or counter-clockwise. Doesn't change with instrument plugged in or not. I've tried different outlets in different places with both amps plugged in to the same and one hums the good one doesn't. Both B100R's are same vintage USA made so probably identical inside. It real low but as a practice amp it's a little bothersome. I'm guessing it's some bias adjustment inside or a cap going bad? Thoughts are appreciated! BTW, I did search SOLID STATE HUM and have already read all the "give it the lyrics and it won't hum" etc. jokes. Funny stuff...no need to repeat here please. THANKS!