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Laser Digital Audio

Discussion in 'Apple TV and Home Theater' started by xArtx, Sep 14, 2013.

  1. macrumors 6502a

    #1
    Hi Guys,
    So I modified a TOSlink to coaxial digital converter, to fire a cheap 1mw
    laser diode instead of the electrical signal.
    Connected that to the Apple TV TOSlink connector, and the laser can be
    received directly by the TOSlink input (to an amplifier) at the other end.

    http://www.youtube.com/watch?v=N5mortSDy1E

    At the other end, my shelf hifi doesn't have any optical input,
    so I use another type of converter (TOSlink to analogue Left and Right).
    The laser can also be shot into an optical cable.

    What's really interesting is that the ATV provides a DRM free digital audio output.
    I'm interested in pulling the ancillary information such as track info from
    the Cirrus decoder chip... this is a bit of a stop on the way :)
    Cheers, Art.
     
  2. JAT
    macrumors 603

    #2
    DRM-free....yes, that is the SPDIF spec. Basically too old to have DRM.

    Kinda neat overall, but why do we need to beam laser across the air with line of sight issues? Digital cables are just fine.
     
  3. macrumors 6502a

    #3
    Just a novelty... It's not like I'm trying to sell it to you :D
    It's a bit of a side step on the way to a digital level meter.
    Apple can't produce any music visualiser, in any device,
    , I suspect because they can't see their own PCM data.
     
  4. JAT
    macrumors 603

    #4
    Come up with a good reason why this is superior to wire and audiophiles may eat it up. Charge at least $2000 per unit. :D
     
  5. macrumors 6502a

    #5
    The TOSlink optical cable is already superior to wire because it's
    not vulnerable to electromagnetic interference.
    Laser would only be superior for applications where you can't use optical cable
    (ie. you can't hang a wire between two buildings).

    For me it's a cool way to test signal (locked and error status) for the receiver chip I'm playing with.
     
  6. JAT
    macrumors 603

    #6
    Are you sure about that? Most audiophiles disagree and would tear you a new one for such a horrible statement. Bow before the wire!
     
  7. macrumors 6502a

    #7
    I wouldn't have thought so. It is the same digital signal inside the CD player
    or whatever device before it is ever transmitted on wire.

    Perhaps it has been shown that optical introduces more errors into the bitstream.
    I'd still be surprised.
    I will be able to find that out by counting errors from the decoder.
     
  8. macrumors 6502a

    #8
    Got the amp today:

    [​IMG]

    It's mostly two radios (AM & SW), a lot of this is insignificant to the amp.

    [​IMG]

    I do need to replace a valve that is in abundant supply and cheap,
    and all electrolytic capacitors, but other than that, should be good to go :)

    The DAC is also my first custom PCB :)
    I have had them manufactured, but never done one myself.

    It is the optical connection that can isolate the modern digital device from the
    high voltage, and unpredictable 1950's valve amp.
     
  9. JAT
    macrumors 603

    #9
    Optical requires 2 extra conversions, so more chance for issues. People like to whine about jitter.
     
  10. xArtx, Nov 16, 2013
    Last edited: Nov 16, 2013

    macrumors 6502a

    #10

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