Tube Preamp Hum

Discussion in 'Digital Audio' started by anothernewbie, Apr 8, 2009.

  1. anothernewbie macrumors member

    Oct 21, 2004
    Deming, New Mexico
    My Presonus DP preamp has slight hum on the tube channels. No hum on the solid state preamp side. It is out of warranty. Have you experienced this problem? If so, what have you done to fix it other than spend big $ on a better tube preamp?
  2. Burtonsnow9 macrumors regular

    Feb 22, 2008
    Hey man, I've played bass for about 5 years now so I think I can help you with this one.

    First of all, I would check all of your connections, like cables, and make sure it's not a faulty one. But really what it sounds like is that one of your preamp tubes is going bad, and so you're getting a humming noise. You can open up the casing and try to reseat the tube (basically take it out and put it back in) but more than likely you'll need to replace it. If you replace it, I'd recomend replacing all of them at the same time for consistent tone, and make sure you get the same type of tube (type, not brand) otherwise it will require more work.

    Hopefully that helps somewhat.
  3. ChrisA macrumors G4

    Jan 5, 2006
    Redondo Beach, California
    This little presonus preamp is not like a bass amp. the presonus amp likey only has one tube and it is likely one of those sub-compact types that is only about 1/4 in diameter and soldered down top a circuit board.

    I think you should put together the smallest system that demonstrates the hum you can. maybe that is just the preamp and headphones? Anyways, disconnect everything you can. Then swap mics, headphones, cables and so on. Prove to your self that the problem sticks with the preamp, no mater what else is connected. Change out wall outlets or source of power (power cube "wall worts") too. If the thing still hums then it is going to need repair. Send it in or if you have the skills and equipment do it yourself. It's likely a 5 cent capacitor that needs to be replaced. but there are very few skilled techs, most will only know how to replace an entire circuit board. So repair may not be economical, even if it's only a 5 cent part.
  4. zimv20 macrumors 601


    Jul 18, 2002
    i have to wonder if the tube even does anything -- is it just for show?
  5. Drumjim85 macrumors 68030


    Oct 7, 2007
    DFW, TX
    I think it's funny there's a tube preamp question in the "Digital Audio" forum :D
  6. michael.lauden macrumors 68020


    Dec 25, 2008
    welcome to the world of tubes!

    make sure your tubes are good, make sure you are plugged into a power conditioner, and make sure your cables are all good.

    if you don't have a power conditioner, try it in a few different outlets to find the cleanest power.

    i hope this helps. but when you use budget equipment you are sure to run into problems like this.
  7. Burtonsnow9 macrumors regular

    Feb 22, 2008

    Nahh buddy, the presonus preamp uses a standard 12AX7 tube, 4 of which are currently residing in the preamp section of my bass head, so it definitely is relevant to a bass amp.

    Now, I would still say that it could be the tube. How old is the unit? And does it have a switch to bypass the tube section, as this would let you decide if it was that or not.

    And I completely forgot to recommend it, but I would also definitely agree on trying a power conditioner out. You need not just a surge protector, but a power conditioner that will filter out unwanted electrical noise. Furman one are pretty standard and can be found on ebay for like $40 (for the cheapest one).
  8. ChrisA macrumors G4

    Jan 5, 2006
    Redondo Beach, California
    Wow I just actually read the user manual. Yes it's a 12AX7 and they'd really managed to shoe horn it in there.

    The manual even says to replace the tube when the sound quality starts to degrade.
  9. Burtonsnow9 macrumors regular

    Feb 22, 2008
    yea man, those preamp tubes last a long time, but once they go it's time to replace it:cool:
  10. Benguitar Guest


    Jan 30, 2009
    I am not a bass player, but I am a guitarist that uses a 1964 Fender 2x12 Bassman. My amp buzzes every once and a while I have found that using too much gain in the amp or on an external effect pedal can cause your amp to buzz or get "fuzzy."

    My suggestion- Turn the gain/or whatever you bassists use to get your "guts" down until the buzzing stops, and if that is too extreme a change for your tone then go with the Noise Suppressor.

    Attached Files:

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