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Audio card INPUTS : Which is better? 1/4" TRS and TS or SPDIF (coax digital)

Discussion in 'Computers / Software' started by jp008, Sep 26, 2016.

  1. jp008

    jp008 Active Member

    Which do you think is better for audio card INPUTS (not outputs):

    1/4" TRS and TS
    SPDIF (coax digital)

    1. The balanced input jack on the audio card is rated at being 104 to around 107 dBA SNR.

    2. We all know the SPDIF input is basically digital 1's and 0's.

    3. Both inputs are 24-bit / 44khz or 48khz

    So.. which one do you think might be better or worse?

    Would they sound different.. and if so, then how?
  2. jp008

    jp008 Active Member

    Just to clarify (since I couldn't edit my post above for some reason)..

    The balanced input jack is 1/4" TRS and the SPDIF input is digital coax 75 ohm.
  3. Boswell

    Boswell Moderator Distinguished Member

    It's not a very meaningful question.

    Assuming you are talking about a proper audio interface and not a computer sound card, the S/PDIF input will have no sound of its own, as the digits pass unchanged through it. Any sonic qualities will be attributable to whatever piece of equipment amplified and digitised the audio signal ahead of the S/PDIF input.

    By contrast, an analogue input (TRS jack in the example you give) will feed an input amplifier of some sort followed by an A-D converter. Both of these components inside the interface may have a sonic quality of their own, and this will be added to (convolved with) whatever was present in the incoming analogue signal.

    If you have a 2-channel high-quality digitising pre-amp, you can feed its S/PDIF output into a computer using a cheap interface that happens to have an S/PDIF input. As long as the interface does not corrupt the digits on their way through, it will cause no signal degradation.

    I would exclude most PC motherboard audio and S/PDIF inputs from this description, as they can cause all sorts of problems.
    kmetal and pcrecord like this.
  4. jp008

    jp008 Active Member

    Interesting. What "piece of equipment" would you say would be good to have "ahead of the SPDIF input" ? Can you give me an example of something you would use personally ?
    I'm assuming this is what you're referring to by "audio signal ahead of the SPDIF input". High-quality digitizing preamp ? Like.. for example ?

    Again, can you give me a good example of something that would have a "sonic quality of it's own" ? In this instance, it would be TRS related though. Something like a PCI card perhaps ? What would you say has good "sonic quality" ?
  5. Boswell

    Boswell Moderator Distinguished Member

    Another question that's impossible to answer without any idea of what you want to record and your budget. Since S/PDIF is a two-channel digital transmission protocol, you would be looking at two-channel pre-amps that have S/PDIF output, an example of which would be the Audient Mico. That particular unit has been discontinued now, but there is still stock around at dealers.

    See above.

    This would be a pre-amp that imparts a recognisable quality to the signal passing through it, as opposed to being "transparent". Transformer-input pre-amps are best known for their desirable sonics. Look at the API 3124+ as an example.

    Your comment about a PCI card is disturbing.
  6. pcrecord

    pcrecord Don't you want the best recording like I do ? Well-Known Member

    @jp008 : You need to give us the whole picture. If I ask which kind of fuel is better for my car and I don't say which car, I'll get various answers.

    What is your audio interface, (make and model) ?
    what do you want to record, vocals, keyboard, drums.. ?
    what other gear would you like to use, outboard preamps or compressors ?

    In my situation, I have Focusrite ISA preamps plugged in my TRS line input of my RME FF800 and I use 2 Universal audio LA-610 which go to a mitek AD96 converter and then to the RME in SPDIF.

    Be aware that using any digital port on your audio interface implies some synchronisation process. either with wordclock cable or via the signal itself. So one of them needs to be the master clock and the others are slaves...
  7. bouldersound

    bouldersound Real guitars are for old people. Well-Known Member

    What's better, a car or a boat?

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