Mesa Mpulse 600 weird sounds?

[M-dawg]

I just bought one of these off of ebay and it came last week (Purple with purple and blue leds) and I noticed weird humming/hissing sounds as I was playing it. The loud hum would increase in volume and my I would lose the volume of my bass tone. I thought it might be the tubes, so I changed them and now have 1 mesa 12ax7 and 1 JJ in there. Probably not the best idea to have two different brands of tubes, I will change that... As I went to play through it again I noticed the same sound but less intense. Anybody know whats wrong?

[BassmanPaul]

Different brands are perfectly fine. Your description could cover many problems and the best way to find which you have is hands on. A trip to a tech is in order.

Paul

[svtb15]

Also try cleaning the EFFECT IN OUT jacks.... Run a 1/4 cable in and out a dozen or so times with the amp offf.. then turn it on and see if it is fixed.
sometimes there may get corrosion on those jacks and they are between the preamp and power section...
Just a guess...

[RickenBoogie]

Yeah, it's all guesswork at this point. Take the amp to a qualified amp tech, and be sure everything's as it should be. That's a great amp, and once fixed, should last a lifetime.