Digital Noise when using spdif on 2408MKII? sync issue?

[jt3_jon]

Hello everyone,

I'm running a computer based DAW and an external signal processor (TC Helicon VoiceWorks) that I would like to connect digitally via the Spdif I/O's on both units, but am experiencing digital noise which I believe is the sound made when units are out of sync (doesn't sound like analog hiss, but has an artifacty quality to it, and its only happens when this unit plays digitally. I've tested the unit with analog and it works fine). Here is my setup.

Dual 2.5Ghz PPC G5, 7GB Ram, OS 10.4.11
Aggregate audio device consisting of Built-in audio (use the digital out from my G5 to a mixer to my speakers) & 2408MKII w/ PCI-x card. I have the "Clock" in Audio MIDI Setup set to the MOTU unit as I was hoping the sync information from my computer would go to my MOTU unit, and then out the Spdif to the TC Helicon unit. The "resample" checkbox in Audio MIDI Setup is unchecked.

The MOTU preferences are set with a "Clock source" of PCI-424 SMPTE. Bank C is my Spdif Bank.

What am I doing wrong? Any ideas?

Thank you in advance for your help and reply,
Jon

[jt3_jon]

Still haven't figured this out. Any help would be greatly appreciated.

[jmadill]

I could be wrong, but I don't think you want to be using the PCI-424 SMPTE as the clock source. The main reason I say this is because nowhere in your message did you mention an external SMPTE source, which would normally be required.

It does sound like a word clock issue ... and I've had more than my fair share.

Try setting the clock source to be INTERNAL which would be the 2408. If you are worried about the G5 audio syncing, it should be fine with this setting.

Another thing to make sure of is that the VoiceWorks is set to clock to the SPDIF, and the sample rate is the same as the 2408. If you can't change the sample rate on the VoiceWorks unit, then set the 2408 to the same sample rate as the VoiceWorks.

Good luck!
-jm