SPDIF sync seems to slip

  • Thread starter Thread starter flanneljammies
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flanneljammies

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I'm getting an intermittent problem using my M-Audio 2496's SPDIF input. Every once in while the sync seems to slip and tracks recorded with the 2496's analog input don't synch with SPDIF tracks. They always start in sync, but sometimes they drift apart. I'm not sure which is correct, but the analog tracks start to get ahead of the SPDIF tracks. Sometimes this happens after 30 seconds, sometimes after a minute, sometimes not at all.

I recorded drum tracks into Vegas using three mics: MXL 603s overheads through an ART DPS SPDIF; and a 421 kick through a DMP3. The M-Audio control panel is set to sync to external SPDIF and the sample rates match at 44.1. I've watched the control panel during takes and the "Locked" indicator never changes.

I've recorded using this setup before without any problems Any ideas about what could be going on now?
 
update

I contacted both ART and M-Audio tech support. ART says it's not a clock issue, because there would be all kinds of digital noise and distortion. They blame latency and "drift" (no kidding!) and tell me to play with my buffer settings. M-Audio copped out and said to upgrade to Window 2000 Service Pack 4 and the latest M-Audio drivers.

I tried recording again yesterday and the drift is really maddening. The tracks recorded to the Audiophile 2496's analog inputs are often off. If I try to slide the track to line up with the tracks recorded into the SPDIF, then it's off elswhere. The drift seems to get bigger the longer I record. I tried messing with the buffers in the M-Audio control panel to no avail. I haven't upgraded to SP4 or driver version 5.10.00.36 yet.
 
In the M-audio panel try choosing Driver mode "Single and in sync", assuming it is currently "independant". That should prevent the s/pdif and anlog drifting apart.
 
That sounds like it could be it. I won't have a chance to check until I get back over to our drummer's house later this week. Thanks, Jim. Stay tuned...
 
problem solved (sorta)

Nope that wasn't it; Single and in sync was already checked.

I spent six hours yesterday trying to resolve the problem. I installed Windows 2000 Service Pack 4 and the latest Delta drivers. This made absolutely no difference. I was able to determine that it was the digital signal that was slipping. The analog were fine. I tried every option or preference setting in the M-Audio Control Panel and Vegas that I could think of. Finally, just as I was about to give up, I turned off the Vegas option to show waveforms while recording. This fixed the problem! It seemed to good to be true. I went back and forth three or four times to replicate and verify. I'm not sure why this would solve the issue though. Maybe there's something about video resources or something. In any event, I think we've got it licked. Forward...
 
OK, it turns out it was a buggy version of Vegas (2.0h). (I know, I know, I should have upgraded years ago, but it's a lot of cake and I don't really need the video stuff.) The slip still happened with the wave forms off, it just took longer to show up. A friend confirms that he had exactly the same SPDIF slip using Vegas 2. So anyhow, I downloaded and installed Tracktion. It's rock solid and has an amazing UI and workflow. It's a truly innovative and groundbreaking product. I'm looking forward to finally tracking our record. yay.
 
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