SPDIF setting

    For me the samplerate is not important but I think that "master only" is a big oversight.


    How would you connect 2 KPAs at the same time using SPDIF? Or if you had another device which cannot be set to slave mode + the KPA?

    Alright, quick feedback.
    I got the Behringer Ultramatch Pro SRC 2496 today and connected it.
    Works to my surprise and to others' expectation.
    Now I've connected my Profiler's S/PDIF Out to the Ultramatch S/PDIF In, the Ultramatch S/PDIF Out to the Focusrite Liquid Saffire 56 S/PDIF In .... and the Wordclock Out of the Focusrite to the Wordclock In of the Ultramatch.


    Input of the Ultramatch is synchronized to the Input 44.1kHz from the Profiler.
    Output of the Ultramatch is synchronized to the (48kHz) Wordclock of my Focusrite.


    Enough success for today, thanks for the push in the right direction.
    Tomorrow I will do a few tests to see if there's a degression of the sound quality due to the conversion and re-sync.


    Cheers,
    Martin

    Great!


    I never doubted that this SRC conversion is possible, but I actually didn't know what company would offer a solution. The chipsets for this are available since quite a time.


    Here is an explaination how it works and why having two masters is not a show stopper with a sample rate converter:
    A SRC converts one sample rate on the input to another on its output. The two sample rates are not related to each other, that is why there is no master slave relation between them. Both input and output have a separate clock.


    Where do these clocks come from? They are either internal or external each. When you have the Profiler as a clock master and the audio interface as the second clock master, then both clocks are external - seen from the SRC.


    As a side effect, the SRC can even communicate with two independend master clocks, that are on the same sampling rate. This is like converting a clock master into a slave.


    +1

    That's nice and all, but it would still be quite practical to have a SLAVE option built-in so that we don't have to buy a large $200 unit just to get it.


    I would appreciate it if Mr. Kemper could answer if they thought about the situation where someone has two "slave only" devices in their setup.

    In my studio, we are recording through a Symphony 8x8 I/O. The Symphony will not allow us to use the KPA as a master sync source as currently configured. If the KPA had a Word Clock BNC connector then we could set the Symphony to use the KPA Clock.


    I really believe that KPA should at least add BNC connectivity for external clocking and syncing if it is only available as the master. Syncing through the SPIDF results in pops and clicks at 44.1 khz.


    Right now, we are recording through analog inputs, but this is not our first choice.

    Wow, this thread has become much longer than I had expected. And I am much wiser too! Thanks to everybody, who has contributed to this thread, not in the least to CK and lightbox. If I will be forced to work on 48 kHz, I know that a simple solution for €159 will solve everything. We'll see where it goes :-).

    Quote from lightbox

    Tomorrow I will do a few tests to see if there's a degression of the sound quality due to the conversion and re-sync.


    Ok, it's been a while since I got these Sample Rate Converters.
    I just want to report that the sound quality of the UltraMatch conversion is less than perfect to put it mildly. Going back to analog output.


    Cheers,
    Martin

    Recorded a short & simple clip ... digital and analog at the SAME time and then moved it in my DAW to play in sequence.


    First one is the digital route with the Behringer UltraMatch set to re-sync to the Focusrite and resample from 44.1 kHz to 48kHz, the second one is analog outputs straight into the Focusrite Liquid Saffire 56. No level adjustment, no compressors, no limiters.


    http://www.wikpa.org/_files/kpa-test-digital-analog.mp3


    I think you can easily hear the difference. The analog recording has much more brilliance, presence, you name it.

    Quote from lightbox


    Ok, it's been a while since I got these Sample Rate Converters.
    I just want to report that the sound quality of the UltraMatch conversion is less than perfect to put it mildly. Going back to analog output.


    Cheers,
    Martin


    I got one of those last year on Ebay. I used it to connect the Kemper to an Axe Fx II for effects until I sold the Axe. I performed some A/B tests (all using SPDIF exclusively) converting to 48khz and bypassing the converter and honestly I don't remember noticing any difference while playing with it.

    [Blocked Image: http://www.wikpa.org/_files/spectrum-difference.jpg]
    I did a spectrum comparison of the two recordings. In an ideal world, the difference image on the bottom should be 100% black. But it isn't. The difference image hasn't even been edited to increase the contrast or brightness.


    If I find the time, I will do this test again and precisely adjust digital vs. analog levels with a 1kHz sine wave first.


    Cheers,
    Martin

    Quote from lightbox

    [Blocked Image: http://www.wikpa.org/_files/spectrum-difference.jpg]
    I did a spectrum comparison of the two recordings. In an ideal world, the difference image on the bottom should be 100% black. But it isn't. The difference image hasn't even been edited to increase the contrast or brightness.


    If I find the time, I will do this test again and precisely adjust digital vs. analog levels with a 1kHz sine wave first.


    Cheers,
    Martin


    That's interesting. Would you mind doing the test again at 48.1 khz and without the SRC converters?


    Also, could your audio cables have a role to play in that? I think whichever way you look at it though, there will always be a difference between a digital connection and an analog connection.

    Quote from nightlight

    That's interesting. Would you mind doing the test again at 48.1 khz and without the SRC converters?


    Hi nightlight,


    I have to agree that there will always be a small difference and to be honest, I expected some clear indication for differences in the higher frequencies. But the difference image shows a pretty uniform pattern over the whole frequency range. That's why I will do another test with perfectly adjusted levels as soon as I find the time.


    I didn't understand your request for another test. I did this test with 48kHz as this test isn't possible without SRC. Maybe it was just a typo on your side and you're asking for a 44.1kHz comparison analog vs. digital? Will try to do this as well, although this requires some configuration changes here. Give me some time to do that. :)


    Cheers,
    Martin

    I cannot agree, that the analog recording (the second) has more brilliance.
    It is slightly louder, thus has more brilliance and even more bass :)
    The slightest difference in loudness renders an A/B comparison impossible.


    The spectrum comparison is also not accurate, as it might not reveal slightest differences without adding additional artifacts.
    Two analog recordings with the same equipment, but taken separately might create the same noisy difference pattern, without revealing a sonic difference.


    There is actually no reason why the Behringer should fail. Behringer might not have the best reputation in audio precision when it comes to analog processing, but an SRC consists of digital standard components that are used by other companies as well.
    A cheap computer will not fail to reproduce music, if you avoid to use its analog audio interface. Nobody has ever doubted this, I think.


    Oops. That's right, I was hoping for a 44.1 khz test, it might shed some light on whether a similar inconsistency exists without the SRC.

    Quote from nightlight


    Oops. That's right, I was hoping for a 44.1 khz test, it might shed some light on whether a similar inconsistency exists without the SRC.[/quote]



    What's with "source code"? Mods might want to look into this.