piezoelectric noise

Discussion in 'General Electronics Chat' started by steve167, Jun 7, 2009.

  1. steve167

    Thread Starter New Member

    Jun 7, 2009
    I've got a relatively high power tube guitar amp that runs at about 20 watts RMS. Recently I've been using a specialized "dummy load" box that allows me to run direct into my mixing board for recording. I noticed that when I have the master volume of the amp cranked to get the desired power tube saturation that my load box actually has a very, very faint acoustical "buzzy copy" of the same notes being played on guitar -- the guitar amplifier itself does slightly as well. Obviously these sounds are not very high fidelity and are pretty quiet -- but are there. Am I experiencing this so-called "piezo noise" that people talk about coming from certain electronic components operated at high voltage? Generally speaking this isn't a problem since guitar tube amps are typically operated at high volume levels through speakers, not load boxes. Even for recording it's not really an issue since it doesn't produce noise in the signal -- it's just acoustical noise you can just barely hear. BTW, we're talking about pro-grade, bulletproof equipment here that is hand made(albeit with PCBs), e.g. Orange, Koch, Soldano.

    Any input is welcome!
  2. PackratKing

    Well-Known Member

    Jul 13, 2008
    This is called .........."exceeding the envelope"

    If this QRM is really objectionable............just do the blunt freakin' obvious.......... turn down the power !!!!!:eek:

    Then again, "rocker" mentality cannot seem to grasp the premise that louder is not better.........:D:rolleyes:
    Last edited: Jun 7, 2009
  3. steve167

    Thread Starter New Member

    Jun 7, 2009
    outside the envelope!?!?! yeah, i like the sound of that!!! funny enough, mike(soldano) has been building legendary guitar(tube) amps for decades and every single amp he builds has the controls numbered and labeled on the front panel to go to 11. they're actually calibrated to go to 11, too, with that extra bit of "spin"

    so anyway, the loadbox I'm using is rated at 50W RMS and 125W peak(for 180 seconds). so as much as i wish i was outside the envelope i don't think i really am. *sigh* but it sounds great! i actually emailed Koch(german manufacturer of the loadbox/attenuator) to find out if it's normal. I'm sure I'll hear back soon.

    just fyi here's the actual loadbox/attenuator.


  4. Audioguru

    New Member

    Dec 20, 2007
    Some ceramic capacitors "sing" with high signal voltages. They also act like microphones for low signal levels.

    Output transformer laminations also "sing" when the level is high.