A few months ago, I bought a used Mesa M-Pulse 600 and I would like to have an opinion on a noise (hum) problem I get with the amp. I play a Fender jazz bass and I know by definition and experience that when you play single coil on a jazz bass, you get a normal 60 cycle hum and I have always lived with this reality. Of course when I play humbucker I dont have the noise. Since I got my M-Pulse, the hum is incredibly loud and annoying. I tough it was my bass, so I have shielded the cavities and the pickups without results. I have tried another jazz bass and I had the same noise, I have tried my bass on another amp and I got the standard hum. In fact, I played a swr sm-400 for many years without that kind of noise. Is it a common issue with the M-pulse? This amp as an incredible warm tone but the noise is so loud that it makes it unplayable. Thats frustrating to get this noise with a hi-fi amp like the m-pulse. Thank you very much for your time.