IMAC i7 to 5.1 surround

Discussion in 'Digital Audio' started by jmunzke, Dec 15, 2011.

  1. jmunzke macrumors newbie

    Joined:
    Dec 15, 2011
    #1
    I have an iMac i7 and an old Sherwood 4 channel analog power amp (2 RCA jacks in and 4 channels out). I was hoping to use the MIDI interface on the iMac to make my iMac a pre-amp and power my speakers with the power amp.

    So far no luck.

    I have a Y cable from the headphone on the iMac to the RCA's on the power amp. I can get stereo but no 5.1

    THE QUESTION: How can I use my imac to play 5.1 with my amp provided the power to the speakers.

    (there is no optical in on the receiver, only RCA in.)
     
  2. blueroom macrumors 603

    blueroom

    Joined:
    Feb 15, 2009
    Location:
    Toronto, Canada
    #2
    What is the model number of your current amp?

    You need an amp with a Dolby 5.1 decoder. They'll usually have an optical input.
     
  3. jmunzke thread starter macrumors newbie

    Joined:
    Dec 15, 2011
    #3
    " old Sherwood 4 channel analog power amp (2 RCA jacks in and 4 channels out)"

    Is there anyway to use the existing sound card in the iMac? Or is there an existing mac compatible sound card that will process the sound into 5.1
     
  4. blueroom macrumors 603

    blueroom

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    Feb 15, 2009
    Location:
    Toronto, Canada
    #4
    Nope. It's a two channel amp. You need to buy an A/V receiver.
     
  5. Makosuke macrumors 603

    Joined:
    Aug 15, 2001
    Location:
    The Cool Part of CA, USA
    #5
    I'm assuming from your description that the amp you have is using Dolby Pro Logic to extract a 4.0 soundstage from stereo audio. In which case, so far as I know, the connection setup you're describing should work--the multichannel should be part of the actual audio, and would be passed out via the analog signal. Sure it's not something in the software chain (I'm not fully understanding what you're describing on the other end) doing it?

    I'm mostly responding because I know for a fact this works with stereo audio (from a lossy ripped CD) output via the optical output; if I set the receiver to Dolby Pro Logic mode, it will correctly extract the lo-fi surround channel from CDs that have it. I haven't actually tested with a pure analog out, but I'm pretty sure it'd be the same.
     
  6. blueroom macrumors 603

    blueroom

    Joined:
    Feb 15, 2009
    Location:
    Toronto, Canada
    #6
    Dolby Pro Logic is not DD5.1, not even close.

    Pro Logic attempts to make a rear channel from stereo. DD5.1 is five speakers (Left, Right, Center, Rear L/R) and subwoofer.

    An A/V receiver isn't that expensive and has the Dolby decoder you need. It's good speakers that'll put you in the poor house.

    If you're just listening to music from CD or MP3's then two channel is fine and for most folks preferred (the extra channels are not part of the original material).
     
  7. jmunzke thread starter macrumors newbie

    Joined:
    Dec 15, 2011
    #7
    Thanks for the input, yes, I have an old 80's audiophile 45 lb stereo amplifier. I was hoping the Imac would work as a pre-amp and my Sherwood amplifier would just boost the signal. In retrospect, the question was probably a bit naive. I have run 5.1 with my tv (and an AV setup). I was just hoping to run 5.1 with this spare amp.
    Sounds like that can't be done.

     

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