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Protecting a PA

Discussion in 'Live Sound [BG]' started by sandman357, Mar 2, 2013.

  1. Hi,
    Sorry this is not a Bass question but a PA question. My guitar player runs his acoustic guitar directly through our board. He had a problem with the jack on his guitar and there was a lot of loud popping that came through the speakers. Now one of them has a bad buzzing sound when low frequencies are played through it. I am looking at investing in a new PA for the band but want to know if there is some sort of filter/noise gate the guitar player can run through to protect the system when he runs direct. Would a DI box prevent this? (He has since gotten his guitar repaired.)

    Thanks for any info.
  2. Borzi_4


    Apr 3, 2012
    Unless you are using an amp made for an acoustic instrument, you probably want an eq of some sort. I have a Fishman pro eq that I always use for upright, but it also works wonders for any instrument I've paired it with. Acts as a good buffer, making the signal easier for the PA to handle.
  3. derrico1

    derrico1 Supporting Member

    Apr 12, 2005
    Charlottesville, VA
    Put a limiter across the main outputs.

    Also, for almost every channel a high-pass filter can be set around around 100-120 Hz. The exceptions are bass, kick, and floor tom—which can still use high-pass, but set lower (how low depends on how capable the PA is).
  4. uhdinator


    Apr 20, 2010
    Use a limiter in front of power amps or powered speakers. Tell the guy to fix his guitar jack before he damages your equipment. I always tell musicians to plug in the instrument/ mic first then connect it to snake/PA last. In reverse when gig is done. Pissed me off when a keys player pulled his cable out of his keyboard first while still attached to the DI box and snake/PA. Had he disconnected DI from snake first it would not go POP/buzzzzzzzzz
  5. jaywa


    May 5, 2008
    Iowa City, IA
    I ALWAYS make a practice to ask the soundguy if I'm "clear" before I plug or unplug my instrument or power up/ down my amp (when using the onboard DI). He will gladly mute your channel if he knows what's coming.

    It's just professional behavior and common courtesy. Same reason to keep your instruments' pots and switches clean and lubed so they don't pop and "scratch".

    This also makes a strong argument for having multiple user controllable mute points in the chain, e.g. A mutable in-line tuner and a mute function on your amp.
  6. Acoustic guitars always sound better with an instrument-specific preamp versus a regular direct box. For one thing, you won't be cranking the input gain way up on his channel, which sets you up for damage as described. Had a sub blown exactly like this.
    In my experience with Fishman acoustic guitar amps, I was blown away. Gorgeous sound with every possible feature included, including a direct output that sounded great.

    And make sure he gets a pedal tuner and learns to mute the signal with it should changing guitars be necessary. Just spent 2+ years working with a guy who had an amazing Mesa Quad Rectifier head and a PRS--just a gold standard electric rig--who cobbed his acoustic signal path together with duct tape and crossed fingers. Destined for success, I'll bet you $50 his acoustic rig is still garbage 2 years from now.
  7. ggunn


    Aug 30, 2006
    Austin, TX
    In a (somewhat) related story...

    I blew up the tweeters in a couple of monitors in an imaginatively stupid way. I had live mic running through the board in my studio into the monitors, and I was on a ladder running a cable overhead. I was pulling a cable, and I felt a little resistance, so I gave it a gentle tug.

    The resistance was coming from where the cable was lying, which I discovered later was between a couple of trim pots on my mixing board. When I tugged on the cable, it turned one of the trim pots all the way down and the other one all the way up, and the latter one (of course) was the channel with the live mic, which immediately leapt into earsplitting feedback. It was a good five seconds before I could get down off the ladder and over to the mixer to shut it down, and by that time the high frequency drivers were toast.

    Chalk it up to lessons learned. :(

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