EXTREME white noise

Discussion in 'Amps and Cabs [BG]' started by sublime0bass, Dec 27, 2007.


  1. sublime0bass

    sublime0bass

    Aug 2, 2007
    Boone, NC
    so i bought a Behringer KX1200 keyboard amp, which i use as a general PA and a small practice amp (it has a 15, a 5, and a tweeter)

    problem is that there is a LOT of noise coming from the rig, and im not sure why. the unit itself is plugged into a power conditioner, and the noise doesnt really go away if i do a line in from my amp as opposed to using the internal gain control.


    is this shoddy workmanship?

    the nature of a keyboard amp?

    or is it a loose something somewhere, or a grounding issue of some kind?



    EDIT: I only paid $125 for it, should I open it up and mess around inside? I'd be willing to ruin it to learn about audio electronics
     
  2. bongomania

    bongomania Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    While the Behr-basher in me would like to think so, it may not necessarily be the case.

    Nope, not that.

    This is the most likely. It's very easy for a wire to break or loosen from a solder joint, for a variety of reasons. Or a bit of wire crossing over from ground to the audio path. Have a tech check it out, or bring it to a Behr authorized service center- they'll probably swap you a new one rather than fix the one you have.
     
  3. hasbeen

    hasbeen Commercial User

    Sep 23, 2004
    Vice President, KMC/JAM USA: Distributor of Ashdown amplification
    I'm not familiar with the amp so I don't know how many channels it has but:
    * make sure if it is a multi channel that the channel you aren't using doesn't have the volume cranked.
    * I assume it has an active EQ section- make sure you aren't cranking the highs/treble.
    * If there are serperate input and output levels, make sure you don't have the output cranked in conjunction with very little input.
    * Tweeter/horn- If it has one, is there an attenuator/level control on it?
    * What bass are you using? Does it have active eq? I'm sorry, you may have mentioned it but does this rig make noise without an instrument plugged in?

    I hope some of this helps.
    Roger
     
  4. Bryan316

    Bryan316 Inactive

    Dec 20, 2006
    Detroit
    My keyboardist has an old beat-up Peavey keyboard amp, prolly 15 years old, and it is a clean, quiet amp. So there's no excuse your Behringer should be noisy and hissy. Either it needs a cleaning and looking over by an amp tech, or there's serious design flaws.
     
  5. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    1: Power conditioners do practically nothing. 2: The source of the noise is the power amp.

    It does illustrate that the adage "You get what you pay for" is true. If cheap gear sounded as good as expensive gear there would be no expensive gear.
     
  6. Bryan316

    Bryan316 Inactive

    Dec 20, 2006
    Detroit

    No greater truth in the world.
     
  7. sublime0bass

    sublime0bass

    Aug 2, 2007
    Boone, NC
    some developments:

    the noise is there whether there is a signal or not. it seems that if i apply pressure to the Channel 2 volume button, the noise goes away. this is all well and good until i put a line signal in, and then its actually a volume cut. so i either have a low volume/semi-clean signal or a high volume (which could just be the nature of the amp) buzzy signal.
     
  8. bongomania

    bongomania Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    It sounds like there's a bad ground connection either where the Chan.2 vol. pot connects to its circuitboard, or at the point where that circuitboard grounds to the rest of the unit.
     
  9. FWIW I've found "hiss" and "artifacty noise" is generally caused by cheap opamps in the signal chain. Behringer is particularly bad for this IME. It's usually TL072's or similar opamps that are widely used. I've had a great deal of success swapping them out with TLE2072's [or TLE2074's in the case of quads] which are TI's top of the line Excalibur chips. They add around 10db of clean headroom which cleans things up really well. The problem with most Behringer stuff is that they use surface mount components which are close to impossible to R&R.
     
  10. sublime0bass

    sublime0bass

    Aug 2, 2007
    Boone, NC
    i used the PA today, running a BOSS RC2 looper into a Nady 10-channel mixing board, and then using the RCA (red & white plugs) tape record out to the RCA tape record in on the PA, i got a perfectly clean signal.
     
  11. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
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