Distortion when synced to S/PDIF

    Hi all!
    I'm connecting Virus TI (desktop) to the S/PDIF input of Motu Ultralite mk3, and the Ultralite's S/PDIF output to Virus' input. AFAIK, in this configuration the Virus should be slaved to the soundcard's clock - however, when I select clock source "Auto", I'm getting a nasty digital distortion. It occurs on any sound (more noticeable on simple ones, like a single osc set to sine wave) and goes away when I switch the clock to "Internal" - but then the S/PDIF input on the Virus stops working! so it's not a solution either. I don't know if the Ultralite's clock is somehow "bad", or the Virus in general has problems with being slaved to external clock? What can I do to fix this situation?


    Could this be related to USB connection? I seem to remember that everything was fine when I wasn't using VC, but it's been a while and I need to confirm this.


    cheers,
    Boris.

    Hi Boris,


    got the same problem with a TI2 Polar. Had it with my TI1 as well - all the time. In short: The Virus cannot be slaved to an external clock via S/P-DIF. I don't know why, but even support has acknowledged that when I asked. However, I have to use it via S/P-DIF when not in sequencer mode because all the analog inputs on my Fireface are occupied.


    My solution: As long as I'm just playing the TI2 outside a DAW, I slave my Fireface to the TI2 (Fireface clock mode set to "Auto sync", so it's NOT the master). It then works perfectly.


    Unfortunately, the Fireface is well known for its tight clock and virtually jitter-free operation. So, for my DAW work, I always have to switch the Fireface back to "Master", since I don't want it to be shaken by the TI's clock (although this might be pure superstition, I don't know how good its clock is).


    Best regards,


    Christian

    You know.. I came across this EXACT issue last summer, summer of 08 when I just got my Virus and tried to sync it to my Echo Audiofire8. Nothing but problems. I didn't get pure distortion like you are describing, but I did constantly get random and unpredictable glitches, pops, clicks and crackles that were not present otherwise. I tried and tried to get this working and eventually said screw it and never went back. Interesting after all this time I am hearing of this again....

    I used the TI2 Polar with my Ultralite and FF400 via SPDIF and usually it worked fine. Sometimes random noise on one channel, but restarting the TI fixed it. THat said, I eventually went back to the 1/4" outs, just seemed like less hassle.

    Zitat von chbaum

    Hi Boris,
    However, I have to use it via S/P-DIF when not in sequencer mode because all the analog inputs on my Fireface are occupied.


    Same here - I'm out of analog inputs on the Ultralite. Also, S/PDIF is less hassle to plug and unplug - just 1 stereo RCA cable instead of 4 mono TS :D


    Zitat von chbaum

    My solution: As long as I'm just playing the TI2 outside a DAW, I slave my Fireface to the TI2 (Fireface clock mode set to "Auto sync", so it's NOT the master). It then works perfectly.


    Unfortunately, the Ultralite does not have an "auto sync" mode, and in "external sync" mode, it won't work unless the Virus is plugged in - no good for me since the Virus regularly goes out to rehearsals and gigs.


    Anyway, this seems like a real problem. I wonder if Access intend to address it in a future OS update, or is it some inherent design flaw?

    Hard to say, I don't know enough about S/P-DIF.


    I always *thought* it should work because I *thought* that there is a sync signal included in the S/P-DIF standard. So what should be the difference who is master and who is slave? However, the TI does NOT work as slave correctly, while the Fireface does.


    So does the TI only not "see" the sync data sent from a master? Then it would be either a firmware issue or a design flaw (the latter could mean that S/P-DIF does not only need a transfer unit but also a sync unit which might not have been included in the TI).


    Or is there a difference between being an audio interface and being a synthesizer?


    Interestingly, the same clicks and pops occur when I connect a mixer with S/P-DIF output to the Fireface: As long as the Fireface is master, any signal from the mixer is distorted. So the problem is not only the TI's.


    Best regards,


    Christian

    The Virus can't be slaved over SPDIF, thats fact. The most other devices with a SPDIF IN should be able to.


    You can still slave your clock to the Virus, in other words is your Virus the masterclock and all other devices receives its clock-signal.
    Alternative you can use VC and slave your Virus to your sequencer over USB. Your sequencer should be slaved to your soundcard.

    Aether, thanks for your reply.

    Zitat von Aether

    The Virus can't be slaved over SPDIF, thats fact.

    Well, if it has the option to be slaved, it should work properly, shouldn't it? I'm going to record an example of the artifacts and ask Access support. Anyway, good to know it's not only my unit's fault.


    Zitat

    You can still slave your clock to the Virus, in other words is your Virus the masterclock and all other devices receives its clock-signal.

    I tried slaving my soundcard to the Virus, but it didn't work - as in, I got no sound at all.


    Zitat

    Alternative you can use VC and slave your Virus to your sequencer over USB.

    I mostly use VC in Live mode, so I still need to connect Virus' outputs (digital or analog) to the soundcard. Or do you mean the USB connection provides an external clock for the Virus?


    Zitat

    Your sequencer should be slaved to your soundcard.

    What do you mean by that? AFAIK, the sequencer tells the soundcard what sample rate it wants to use (I stick to 44.1 btw) and then just keeps feeding it audio buffers. With all this happening automatically, how can I "slave" it?

    Dear Boreg,



    Quoted from "boreg"
    Well, if it has the option to be slaved, it should work properly, shouldn't it? I'm going to
    record an example of the artifacts and ask Access support. Anyway, good to know it's not only my
    unit's fault.


    Answer:
    Usually that should be right, not all hosts/outputs supports the same SPDIF clock.
    Both I/O's have to get its syncs phase for a well working sync together. And they can't.
    Your SPDIF outputs of MK3 can't get the right sync with Virus in this way,
    cause each sync phase has its own way. SPDIF is not precious as WordClock is.


    damn i need a WC on my Virus...!


    Be sure to disable the SPDIF input of your Virus during feedback in your audio schema.
    In worst case the audiostream from SPDIF comes with ugly crackles.




    Quoted from "boreg"
    I tried slaving my soundcard to the Virus, but it didn't work - as in, I got no sound at all.


    Quoted from "boreg"
    I mostly use VC in Live mode, so I still need to connect Virus' outputs (digital or analog) to the


    soundcard. Or do you mean the USB connection provides an external clock for the Virus?


    Quoted from "boreg"
    What do you mean by that? AFAIK, the sequencer tells the soundcard what sample rate it wants to


    use (I stick to 44.1 btw) and then just keeps feeding it audio buffers. With all this happening


    automatically, how can I "slave" it?



    Answer:
    A Sync/Audio schma for example:


    ASIO/CA/other driver: MK3 Firewire
    Sync schema:
    Virus synced to Sequencer (auto/USB)
    Sequencer synced to MK3 (master)


    Audio schema:
    Virus I/O (auto/USB) to Sequencer
    MK3 I/O Sequencer


    For Atomizer Bus:
    Analog-Input Virus




    for recordings you can may try those for bounces.


    ASIO/CA/other driver: Virus TI USB
    Sync schema:
    Sequencer synced to Virus (USB/SPDIF, internal if able)
    MK3 synced to Virus (SPDIF,if possible, probably not)


    Audio schema:
    Virus I/O (auto/USB) to Sequencer(s) > Bounce
    MK3 I/O Virus analog, SPDIF if possible


    For Atomizer Bus:
    Analog, SPDIF (same sync as sequencer)



    greets Aether