Buzz noise through venue PA

edited January 2017 in Support and Feedback

Hey. Running cello and pick up through berhnger istudio, Loopy HD- Audiobus-amplitude acoustic, out an amp to practice, behringer fcb 1010. There's a bit of buzz in the amp, not bad, but we did an advance sound check at the venue yesterday and it's pretty bad through the pa. Trouble shot a bunch and sound guy did great with it, but still there. Not grounding we think. It's an older ipad gen2 if that may be it. Would be nice to clear up. Any ideas?


  • @berimba - I couldn't find a manual for the istudio, so I have a few questions. Is the istudio running on batteries or wallwart/ac Adapter ?

    You are basically feeding the line level stereo out from the istudio ( dual 1/4 TRS balanced OUTPUTS) into the venues PA system, correct? My first thought would be that this connection is not correctly made. Hopefully the Sound guy was aware of the balanced 1/4 TRS output. How were you connecting to the amp for practice, does the amp have a balanced input or did you use and adapter/impedance marcher/ DI box ?

    just some thoughts, many of which you may already have tried.
    I would break it down if possible and check :

    • try just the istudio ( Cello pickup not connected) to the PA ( Loopy playing through AB and AmpliTube Acoustic, and also, just a clean audio recording played back). Is the buzz still there, same level?
    • try the cello pickup connected ( is it a piezo/contact pickup or microphone type?) just running through AB, then just through AmpliTube Acoustic. Can you connect the cello pickup directly to the venues PA? Of course the last one, would probably not be relevant, as it would be connected to a different type of input connection on the PA.

    Depending on what, if anything makes the buzz disappear/decrease, one should be able to narrow down the possible source of the problem.

  • edited January 2017

    Thanks for the response.
    Yes to AC.
    Yep, stereo 1/4 outs that he was aware of. In the amp just use the mono R. And we tried a couple DI's (cello micd too). Even split the cello separately to rule out the pick-up, which it did. Yes, contact one.

    Sometimes I wonder if it's something as random as a full charge vs. charging while running?


  • @berimba - last thought (at the moment). try the Headphone connection on the istudio with monitoring turned off. Should be the same audio signal as the Main L/R, but via a slightly different internal istudio route.

    Also, have you tried it with batteries in the istudio, would rule out the a noisy (cheap/defective) power supply, but won't rule out the internal voltage regulator. Behringer is not exactly high end equipment, not bad, but....

  • I'm by no means an electrician but it seems to me that using quality shielded cables at every stage is a prerogative. You'll find that the buzz amounts will vary from venue to venue, mostly due to the quality of their sound system/leads but most importantly grounding of their electrical system.

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