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Ground Noise from PatchBay/Midi connection

Discussion in 'PBC General Discussion' started by JamesCardoza, Sep 12, 2018.

  1. JamesCardoza

    JamesCardoza
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    Hey everyone,

    I’ve recently noticed a slight buzzing/clicking sound in my rig. The sound is only heard when my volume pedal is up all the way, but is present when no pedals are on in the loop. I checked all my cables, and terminations were fine, and then noticed that the buzz/clicking goes away when I disconnect any of my Midi cables, but specially when I disconnect a midi cable from my in/out American loopers PatchBay on my board. The PatchBay has five neutrik TRS 1/4” jacks and one 5pin din, as well as a stereo/mono sum switch. Could the PatchBay be causing a ground loop in my rig, and If so how can I get rid of it? I’ve attached a picture of my rig for reference, and the Dropbox link below links to an MP3 of the sound, and shows the buzzing going away when I disconnect the midi cable from the PatchBay. https://www.dropbox.com/s/od49svi5ngct6rf/grounding isse .mp3?dl=0

    Thanks!

    Jimmy
     

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  2. rjmmusic

    rjmmusic
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    Are you using MIDI clock? If so, that's probably the MIDI clock signal bleeding into the audio. There's probably not enough shielding between the MIDI wires and the audio wires in the interface. It could be grounding as well, but it sounds more like MIDI data to me.
     
  3. JamesCardoza

    JamesCardoza
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    I am using the PBC as midi clock source. Would The noise subside if I opted to not use the clock from the PBC?
     
  4. rjmmusic

    rjmmusic
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    If my theory is correct and it is coming from the clock, it will only subside if you don't use MIDI clock at all. It would be a good experiment to try turning off MIDI clock and see if the noise goes away.
     
  5. JamesCardoza

    JamesCardoza
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    thanks! I’ll take a look as soon as I can.

    Along with that, if the clock is the issue, is there anyway to isolate it so that it’s not an issue? I run multiple devices, all of which utilize midi clock for tempo sources.

    Thanks!
     
  6. rjmmusic

    rjmmusic
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    Assuming that clock is the problem, the next thing to do is see if it is the interface. Route your MIDI so it doesn't go through the interface at all, see if the noise goes away. If that works, then keeping the signal out of the interface or improving the shielding inside the interface would be your two choices.
     
  7. JamesCardoza

    JamesCardoza
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    By interface you mean my PatchBay right? Just wanted to make sure. I know as of now that the noise goes away when my MIDI is not connected to the PatchBay at all, apart from that the rig is VERY quiet.

    Thanks!
     
  8. rjmmusic

    rjmmusic
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    Yes, patchbay. Sounds like the patchbay needs some better shielding inside. MIDI shielding is really important, MIDI signal levels are 5 volts, compared to a guitar signal that's a fraction of a volt. Lots of opportunity for noise to broadcast. In most cases, MIDI data is only transferred for a split second, right when everything else in your system is switching anyway, so the noise isn't noticed. But with MIDI clock, it's transferring messages all the time, causing continuous noise.
     
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  9. mcvittym

    mcvittym
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    Having read this thread, I am pretty sure I'm getting MIDI clock noise, but only if I either (1) unplug the guitar from the input on the patchbay or (2) disconnect the patchbay from the input ('In 1-4') on the PBC. When I switch off the MIDI clock on the PBC, the noise stops. I get the noise even when all the audio loops are switched off. Fortunately when my guitar is plugged in there is no noise. I can't help feeling that something is wrong somewhere, however. Any quick and easy suggestion borne from experience as to what the cause may be?
     
  10. rjmmusic

    rjmmusic
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    I'm guessing that your guitar input jack isn't set up to ground itself when the guitar is not plugged in. Add that, and you'll probably fix the noise issue.
     
  11. mcvittym

    mcvittym
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    Thanks, Ron!
     

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