SPIDF vs. Analog a Visual Comparison

  • Hey guys, I've been considering replacing my Digi 003 with an Apollo Twin Duo, but the more I think about it the less I think it's worth it since I am recording using the SPIDF output, which should be the same 1's and 0's in any device.


    I also ran a test recording the same session in ProTools, two tracks:
    - One SPIDF mono in (Master)
    - One Main Output (Analog) mono in (Master)


    This is what I found:
    - Absolutely no noticeable difference (I know purists will hate this, but to my ears the signal was the same, not even a marginal difference)
    - There was a 0.006 second LAG on the DIGITAL signal... yes, on the SPIDF signal (to my surprise)


    Here are some pics, Gtr1 is the SPIDF, Gtr2 is the Master Out Analog.


    The overall visual of the tracks
    [Blocked Image: https://i.imgur.com/5ojItDR.png]


    Here, we see there's a difference in the time the signal hits the CPU (the SPIDF signal is slower)
    [Blocked Image: https://i.imgur.com/KLC3QGN.png]


    A close up highlighting the distance between the two identical points tells us the difference in time is 0.006 seconds (is this even significant!?)
    [Blocked Image: https://i.imgur.com/ofStKKf.png]



    Spectrum Analyzer to see if there's a difference in frequency (I couldn't get the levels PERFECTLY the same so one will be louder than the other, the idea here is that the frequencies are identical)
    [Blocked Image: https://i.imgur.com/QnqAbc8.png]


    So, in conclusion, the difference is marginal and it doesn't really matter if you go analog or digital if what you are after is getting 99% of the way there and making music (e.g., focusing on the actual song, playing, songwriting, creativity). Don't get stuck because you find different forum members arguing about digital vs. analog and about this 0.006 second difference. Just make music! :)

  • Weirdly one would assume that the necessary conversions would cause the ANALOGUE path to have some latency and be ‘behind’ the all digital.


    But I agree that there’s no sonic reason to prefer one to the other IF your A-D is of high enough quality.
    And one has to assume it IS because you’re recording everything ELSE through it!

  • Always said this, hence my decision to use analogue only.


    The S/PDIF's latency is surprising.

    I have lower latency on SPDIF than analogue


    But soundqualitywise there's no difference to care about at all.
    Basically go with what suits your needs the best.


    Personally I have this setup:


    1. SPDIF R - amp tone <--- recording
    2. SPDIF L - DI track <--- recording
    3. XLR Main out L <---- direct monitoring through my interface straight to speakers, so I dont have to go through my DAWs monitoring latency.


    This works great for me! :) I never record stereo.

  • Being as guitar is mainly a midrange instrument, the analogue seems fine to me. You'd have to possess some bad quality converters to see the difference. The previous limitation to SPDIF meant that on 48k albums I could never use it anyway.

  • Was your spdif output set on 44.1khz ? Otherwise, assuming the kpa is still running at 44.1 internally, all other frequencies coule lead to a latency due to the sample rate convertion

    Yes, spidf output was set on 44.1khz, the Digi 003 clock was to external (the Kemper).


    As I understand from other input, the difference in time (latency) was due to the compensation the system does since the 003 is integrated with PT12 it knows exactly how much time to compensate for (and it over compensates), while it is less sure of the spidf conversion.


    The point remains the same though, let's focus on making music rather than argue if anlaog or digital is better :)

  • There are other arguments for using S/PDIF than just fidelity. I use digital on my Kemper, yet I use analog on my Virus.


    Is there a huge sound difference between S/PDIF and analog? Not really. But there are a LOT of things along the way that can change that. Bad cables, RF interference, dirty contacts, accidental phase issues, etc.


    Introducing some unnoticed hum or analog induced distortion in to the signal will add up after stacking the tracks.


    On the other hand, S/PDIF tends to either work or not work. And when it's not working it's REALLY obvious.


    Then there's the personal OCD factor for us anal types. I just don't like the idea of added conversions. So sue me.

  • Maybe I'm doing something wrong but I always seem to be futzing more with levels when I go analog, but with SPDIF most of the profiles don't distort from too much level.


    I also like having less cables, I'm just a home studio player always through the same setup. 2 cables for SPDIF will take care of most of my needs and save some inputs for mics and cowbells.

    You know I'm born to lose, and gambling's for fools
    But that's the way I like it baby
    I don't wanna live forever

  • My entire approach toward digital recording, is that once it's 'In the box' it stays there until it's played back on someone's personal audio player, computer, or home stereo.


    Once my guitar is converted to digital it stays digital (via SPDIF) until playback of the final mix.

  • Eyeballing waveform representations in a DAW is not a meaningful measure of audio degradation through multiple conversions between analogue and digital formats. It is a bit like dipping a glass in a water source and holding it up to the light to assess its safety for drinking.


    If you are satisfied with the audio after two extra conversions well - fine - use that. If you care about the actual fidelity to the source you need to use appropriate measures to analyse the degradation induced by the extra conversions.

  • Spectrum Analyzer to see if there's a difference in frequency (I couldn't get the levels PERFECTLY the same so one will be louder than the other, the idea here is that the frequencies are identical)
    [Blocked Image: https://i.imgur.com/QnqAbc8.png]


    So, in conclusion, the difference is marginal and it doesn't really matter if you go analog or digital if what you are after is getting 99% of the way there and making music (e.g., focusing on the actual song, playing, songwriting, creativity). Don't get stuck because you find different forum members arguing about digital vs. analog and about this 0.006 second difference. Just make music! :)


    There appears to be less frequency content on the SPDIF right at the low end, as well as at the 200hz mark. Doesn't look all that close to me.

  • A friend of mine once posted an example of an audio file original and a copy he had reconverted 50 times. They were near indistinguishable.


    If you’re that worried about the quality of your converters get BETTER converters.



    OTOH, like many audio professionals I have a high quality master clock on my system and it made a massive difference in the sound quality of my converters.
    So the chances of my using the Kemper as master clock instead are, lemme think... nil.