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Hum problem with my m-pulse 600

Discussion in 'Amps and Cabs [BG]' started by Franky, May 29, 2003.

  1. 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 don’t 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. That’s frustrating to get this noise with a hi-fi amp like the m-pulse.

    Thank you very much for your time.
  2. KenToby


    Aug 15, 2002
    If you get to the point where you want to sell just say the word :)
  3. I have an M-Pules 600, and have had no problems at all. Never heard any hum from it.

    Have a techie take a look at it. Good luck.
  4. Is the amp noisy already by itself? Meaning, if you turn the amp fully on without plugging in the instrument, is the noise near the one you described?

    I hear Mesa has a great customer support. Why not e-mail them about this.
  5. Ian Hall

    Ian Hall

    May 31, 2002
    Yeah something funny is definitely going on- mine is dead silent even with the gain cranked. As stated above, Mesa's service is great.. Give em a ring.
  6. DaRange


    Mar 12, 2001
    Minneapolis MN.
    I had a problem with the input jacks on my impulse 600 making a loud buzzing spray contact cleaner cleared the problem right up. If that dosen't help You should contact mesa.
  7. I went to guitar center to buy a Mesa 400+ today..But they had to order it for me. So I needed an amp for tonights gig, and they let me borrow an M-Pulse 600 untill my head comes in.. I gotta say I'm impressed with the tone and volume of this head. I could only imagine how good my all tube head is gonna sound..MESA RULES \m/:bassist:
  8. before you go see a tech,try changing out the tubes.there are only two pre-amp tubes(12ax7)that may help and,its a cheap and easy fix..if that don't work,then bring it to a tech.
  9. Thank you all for the comments.

    I have no noise when my bass is unplug. I have emailed Mesa and the first thing they asked me to do is swapping the tube. That's what I did (with another pair of 12ax7)without results. The noise is mostly present when I boost the gain and when I crank my bass volume. This weekend, I also got a loud "screaming" noise comming from the speaker and it really scare's me.
    I have shuted down the amp, restart it and it was ok. I think there's really something wrong in it.