Output analog and Spdif at once?

    Hi,


    Is it possible to combine Analog and S/pdif together for recording? I'd like to use the Kemper 2 main OUT L/R for FX only (delay/reverb wet) and s/pdif forDI and stack (Git/Stack).

    Quote from lk_bill

    Actually, got my reply from another forum read.
    It's possible, yes, but there is phasing issue when combining the analog and spdif... ???

    Yes, since the conversion of the analog (both DA in kemper and AD in your soundcard) takes some time, there will be a time difference - hence phasing. THat's all there is to it, though. What will you use it for?

    Just pass a string pluck or sharp muted pick through the KPA's S/PDIF as well as analogue outs to your DAW, Bill. Better yet, you could edit a sound to create a super-short spike that has a more-obvious-and-specific attack point (and end if you chop the tail too); this'll make it a breeze to align. You might as well send this spike through the front (guitar) input of the KPA, just as if you were playing as-per the first suggestion, 'cause quality isn't an issue here; as long as you can see the waveform in your DAW once recorded, you'll be good-to-go.


    You can measure the signal-alignment difference visually by nudging, say, the analogue track's waveform backwards in time 'til it lines up with the S/PDIF-sourced one, counting the number of samples / milliseconds you've had to offset it by. Your DAW should allow you to display samples or milliseconds as the data-display type.


    Alternatively, you could play the tracks side-by-side and use a delay plugin on the S/PDIF one, nudging it ms-by-ms until they're no-longer sounding phasey. The reading you end up with is the amount by which you'd need to bring the other track (analogue-sourced one) backwards in time.


    By my estimation you'd probably be looking at somewhere from 1 -> 3ms difference between the two tracks. The amount you determine in the end should be noted and then applied, whether through track-waveform nudging, delay plugin or even an alignment one, if you have it (few do), to all KPA-analogue-sourced tracks in the future, but only when you're running them alongside S/PDIF-sourced tracks. That said, if the signals are different-enough (dissimilar amp tones), you may well not notice any phasing at all; identical waveforms pushed forwards or backwards in time will cause the effect (cancellation), but as you can imagine, if the waveforms look (are) different from each other, consistent phasing is gonna be hard to produce.


    Bottom line: If you're reamping using different amps, I think you'll be OK, otherwise slide the analogue-sourced track/s backwards in time.


    EDIT:
    Martin thankfully reminded us of the KPA's "Constant Latency" feature. For my suggestions to work reliably, this must be enabled.

    In addition to the other posts:
    Make sure you switch your Profiler to "Constant Latency" which can be found in the SYSTEM menu, page 4/18


    The overall latency of the Profiler will likely increase a bit but at the same time it will be "constant" ... you measure once and you can always use that value in the future (as long as the Profiler is set to "Constant Latency". If this option is switched off, the latency changes slightly depending on the effects used.


    Cheers
    Martin