extra latency using SPDIF

  • Hi

    I have just got a (used) Kemper and I am happy with it !
    I have a question about recording from SPDIF versus analog output.

    I have simultaneously recorded the same signal ('Master stereo') from both outputs (SPDIF Out and Main Out) with the same USB audio interface (NI Komplete Audio 6). The track recorded from the SPDIF output is 3.5ms later than the track recorded from the analog output. Do you know where this extra latency comes from? the Kemper? my recording system? Do you experience the same?

    Also, I have noticed a short extra latency when I use the SPDIF Input versus the analog Return Input. When reamping a signal, those extra latencies add up. So I end up with about 8ms of additionnal latency just from using SPDIF instead of analog input/outputs. I can deal with it, that's ok, but I am wondering whether there is something wrong with my setup. I initially thought that I would have less latency using SPDIF.

    Thanks a lot

  • Same latency delay with spdif here. I had measured it, forget how many samples it was. Enough so that you can hear it, if you listen to the analog output and the Spdif output at the same time, it's enough that you can hear phase/ comb filtering. I gave up on using spdif because of that, there seemed to be no 'benefit' of recording that way, tonal or otherwise. My playing is rough enough as it is, any extra delay I can avoid can't hurt!

  • I have both sets of inputs on my Focurite 18i20; Line L+R from main and spdif git/Master Left. Asio at 16 samples 44.1Khz 24bit.

    Indeed, I can confirm this behaviour with the latest firmware 5.4.1

    Main line inputs arrive first, then, spdif.

    spdif "git" which is on the left spdif channel arrives about 1/2 faster than the difference between line and spdif "Master Left".

    This is with a profile with 3 effects in the first 4 blocks before amp.

    However, if I then turn the 3 effects off, then, the behaviour is the same except the spdif "git" arrives about 7 times later than spdif "Master Left vs Main outputs.

    Weird behaviour. I tested this last year and in 2016 and I'm sure spdif was faster than using analogue cables.

  • SPDIF should be faster, but some audio cards and DAW's incorporate "latency compensation" which attempts to line up all inputs for recording in order to minimize phase issues. This is typically more related to fx either on the card (e.g. UAD) or in your DAW's inserts section than anything else.

    The first thing to do is to try and ensure any such setting is disabled as you're getting the raw data without an added delay from the card or in your DAW. For that you'll have to check the manuals I'm afraid.

    If all latency compensation is disabled then it's a matter of testing with multiple interfaces to check again, and finally it becomes about testing the Kemper and it's own effects.

    I can't see any good reason why the Kemper would have a different (or slower) output from SPDIF than analog, traditionally it has less to do.

  • some audio cards and DAW's incorporate "latency compensation" which attempts to line up all inputs for recording in order to minimize phase issues.

    I guess you could test this by doing a reamp, using each kemper output in turn (not simultaneously), and not having armed all the tracks?

    You could even record to the same track twice, just changing the input on the channel strip in the DAW.

  • My firmware is also latest 5.4.1
    I used Cubase LE8 with ASIO buffer 256 samples. Sample rate = 44.1kHz / 24 bits / externally clocked
    I tried to disable any kind of latency compensation (that I am aware of), but it is still the same.
    I tried to record one track at a time, still the same.

  • @Karl what AISO buffer size are you running on the Scarlett?

    16 samples, as low as it will go.

    Here are my settings in Reaper;


    Here is Kemper Profile with FX on;


    Here is Kemper Profile with FX off;


  • I always use SPIDF with the Kemper and I've had no latency whatsoever. Are you sure your have the master word clock set for the Kemper? If not you'll get all kinds of latency issues as well as errors. In fact I only experience latency when recording using the analog outputs.

  • I don't know if this thread is still active but I have something that may help. I plugged my kemper in and had this very issue. Because of this I found this thread. As a control i thought i would try this with my helix.

    The EXACT same issue happened with my helix. (and i mean down to the same milliseconds). Also at time of posting this im using the generation 3 8i6. I dont believe this to be a kemper issue. I believe this to be a Scarlett issue as that is what i use as well.

    Hope this helps

  • I checked this again a few days ago with my RME Fireface 400. I did a reamping loop and recorded spdif and main out simultaneously. At 44.1 kHz, spdif arrives around 1 ms later than analog. Interestingly (and that is why I was measuring), at 96 kHz, spdif is half a ms later still that at 44.1 kHz (1.5 ms later than analog in total). When I measured a few months ago, I measured higher additional latencies with spdif at 44.1 kHz, around 2-3 ms. I did not investigate wether this has to do anything with the specific patch (I used the same patch in the latest comparison, but a different one in the first).

    It would be interesting if tech support has anything to offer on this subject!