Noise problem with pre/power setup

Discussion in 'Amps and Cabs [BG]' started by 8_finger, Aug 19, 2003.

  1. 8_finger

    8_finger Supporting Member

    Jun 1, 2002
    Baltimore, MD
    The setup:
    Warwick Fortress One 5 (EMG pups, MEC pre)
    EBS-1V2 preamp
    Yamaha P3200 power amp (2x 440W @4Ohm)
    EBS 210 cab (400W @4Ohm)
    I use only one channel of power amp

    The problem:
    When I play my pick-ups pick up noise from the fan of the power amp (this particular model has 2 fans on the front side of the amp).

    This problem occurs when I'm cca 1-3ft in front and facing the amp. The noise is really noticable when I'm playing. The noise was turned down a bit when I lowered pick-ups.

    Does anybody know how to solve this problem?
  2. 8_finger

    8_finger Supporting Member

    Jun 1, 2002
    Baltimore, MD
  3. redneck2wild


    Nov 27, 2002
    Memphis, TN
    There are a number of areas that might be causing noise. Here are a few you might check.

    Is there a grounding problem?
    Lack of a ground wire can cause noise problems.
    Miswired outlets can also cause noise problems.
    In either case, the electrical wiring needs to be fixed.
    Radioshack sells a AC Outlet Analyzer that will detect a ground fault:

    Does either the preamp or poweramp have a ground lift switch that is enabled?
    A ground lift switch can sometimes reduce the noise caused by a ground fault but using one can cause other noises and/or electrical hazards.
    I would not use the ground lift switch.

    Is everything in the rack gounded?
    One item not grounded properly can cause noise problems.
    Isolation Tabs:

    Do you have single coil pickups?
    Single coil pickups tend to be noiser than humbuckers. This is more so the case if whatever the bass is connected to is not grounded properly.
    Some Basses with 2 single coils are wired to act like a humbucker when both are fully on (less noise).

    Is you bass properly shielded?
    Check the Contol cavity of the Bass to see if there is shielding inside. You can purchase shielding material from or some music stores.
  4. 8_finger

    8_finger Supporting Member

    Jun 1, 2002
    Baltimore, MD
    thank you for the help
    I dont think it's grounding problem
    but just to be on the safe side I'll check everything on the list
  5. mikezimmerman

    mikezimmerman Supporting Member

    Apr 29, 2001
    Omaha, Nebraska
    The other problem I run into is simply that the output transformer of many larger power amps puts out a lot of EM radiation/noise, and if you stick a bass too close to the transformer that noise gets picked up. Additional shielding in the bass can help eliminate noise picked up in the control cavity, but you can't really shield the front of the pickups. (You're facing the amp, right? You need to be facing the audience! ;) )

  6. 8_finger

    8_finger Supporting Member

    Jun 1, 2002
    Baltimore, MD
    Mike I think you definetly have a point there, I looked inside the Yamaha and the transformer is located in front of the amp between the cooling fans. Lowering the pickups seems to have almost completly solved the problem - now it occurs only if the pickups are less than 1 ft and facing the amp, when I turn them away noise stops.
    Just to be on the safe side I'll chekc the additional shielding for the bass.
  7. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    If you get coupling between the output transformer and the pickups, that could be very bad. Essentially, it would be like feedback, only at ultrasonic frequencies. It could burn out various components, tweeters (if you have them in your cabinet), et al.

    Watch out for power transformers. They tend to emit a hum field. Toroidal transformers are better in this respect than other common types, but they still emit noise.
  8. 8_finger

    8_finger Supporting Member

    Jun 1, 2002
    Baltimore, MD
    This must be it - the noise is almost non existent when I turn down the tweeter and cut highs on the preamp. Thanks for the info. I'll just keep my pickups away from the transformer.