iMac 3.5mm Line Input Pre-Amp?

Discussion in 'iMac' started by elithrar, Sep 20, 2013.

  1. elithrar macrumors 6502

    elithrar

    Joined:
    May 31, 2007
    #1
    I'm looking for a 3.5mm microphone pre-amp so I can plug a 3.5mm mic into my 2011 iMac's line input.

    USB microphones aren't a solution for me unfortunately as my iMac suffers ground loop issues and short of betting > $200 (typically more) on a power conditioner I can't safely resolve the issue. Old house, HAM radio operator down the street on a low freq, etc.

    Note that I've tried a powered USB hub to no avail. I assume an external USB sound card would suffer the same problem.

    (so 3.5mm it is!)
     
  2. BrianBaughn macrumors 601

    BrianBaughn

    Joined:
    Feb 13, 2011
    Location:
    Baltimore, Maryland
    #2
    Sounds like your getting interference on anything you plug into the wall. I'm wondering why a pre-amp would be any different, unless it's battery powered.

    My experience with a ground loop was that I got a hum when audio was connected from a device plugged into a different circuit. Plugged into the same circuit as the computer eliminated the hum.

    I also had some noise once on my powered audio monitors that was eliminated by putting "ground floats" on the plugs.

    What is the brand/model of your mic?
     
  3. elithrar, Sep 20, 2013
    Last edited: Sep 20, 2013

    elithrar thread starter macrumors 6502

    elithrar

    Joined:
    May 31, 2007
    #3
    The kicker is that the headset is USB powered. No external supply whatsoever. So I can't use cheater plugs on the power supply (because I won't use on one on the iMac) and the HumX is only available for 110VAC/60Hz and I need 240VAC/50Hz.

    A cheap-ish ($100) pair of Skullcandy SLYR's, thanks to this Head-fi guide. They are just for gaming/voice comms: I have a pair of Ety IEM's for serious listening.

    I have a pair of Steelseries 'phones that have 2x 3.5mm jacks, however without an appropriate mic pre-amp the microphone won't work: the iMac's line in is unpowered, and most pre-amps give +48VDC, not +5VDC. This won't be friendly to the headphones.

    I've been recommended the GreenKey USB isolator, but I'm concerned it might limit the current draw too much to work with a headset.
     
  4. elithrar thread starter macrumors 6502

    elithrar

    Joined:
    May 31, 2007
    #4
    I've solved this with a Creative X-Fi Surround 5.1 Pro + Soundflower (https://code.google.com/p/soundflower/) to allow me to control the volume with the standard OS X controls/keyboard.

    The X-Fi doesn't exhibit the "hum" I suffered from over a set of USB headphones (which had their own integrated soundcard) and it obviously provides the correct "PC-style" +5V microphone input.

    Cost me $86, which is cheaper than the USB isolator—Firestone indicated it wouldn't be a good solution as the current draw limitation would likely stop most headsets from working.
     

Share This Page