UMC404HD noise issue, only through speakers

  1. #1 by Justin Morell on 07-05-2018
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    Posts: 1

    UMC404HD noise issue, only through speakers

    I'm using an UMC404HD with an iMac. It's connected via USB of course. I have playback outputs 1&2 connected to an amp via unbalanced 1/4" connectors. I hear a constant noise from the speakers that sounds like some kind of RF interference. It isn't a hum so much as a fizzy, buzzing kind of noise. It isn't blasting, but it's enough to be distracting during a mix. The noise reamins at the same volume regardless of where I set the "main out" level. I do NOT hear the noise through the headphone output. I have tried:

    Changing the cables from the interface to the amp
    Changing the amp
    Changing the USB cable
    Connecting to a different USB port
    Connecting the AC adapter to the interface and powering it that way (while still connected via USB)
    Moving the interface to a different location, farther from the computer

    None of these things improves the situation. Any ideas on how I might troubleshoot this? Thank you,