Hi, I was doing a google search for advice and came upon this forum. I have a PM-1.5 amp and lately, there is a buzz when I put it on that switches to a really loud hum through the speakers. At first I thought it was a grounding issued and put the amp and mixer on a different circuit than the guitar amps but that didn't work. I pulled the jumper off the ground and it didn't help. I have unplugged everything but the speakers and that didn't work. I tried different speaker cables - no luck. I have even tried to go from the 3 prong plug to a 2 prong adapter to take the ground out and it didn't work. Nothing seems to get rid of the noise. When I have band practice, the vocals are as a loud as normal through both mics but in between songs, the hum/buzz is unbearable. Help!