G5 optical into 192 - Distortion & Clocking errors

[Polaris]

I've run out of ideas and before I kick this G5 down a flight of stairs, I thought I would run this by the DUC to see if anyone else has experienced this problem:

We are routing the G5 optical S/PDIF into the enclosed S/PDIF on a 192 io and using an aux input to monitor the mac. When auditioning SFX (or playing iTunes or QT files etc.) we are getting garbage (anywhere from mild distortion and clicks to full scale clocking noise and muting) out of the mac. Has anyone else experienced this before? These are some of the fixes we have attempted with limited success, but the noise always returns:

Swapped optical cables
Set AudioMidi Setup to 2ch/48kHz/24bit (our sfx are 48kHz/24bit networked files).
Hooked up optical cables in both directions and tried external clocking the G5 (G5 stays locked to external).
Tossed all Digi, Coreaudio & system audio related prefs
Zapped PRAM
Reset firmware in 192 io
Tried all the various clock & pull up/down settings in PT

What's even stranger is that the noise increases with the mod level and decreases on the silences in between. I would have assumed that clocking errors would have continued. This routing was working fine under OS 10.3.9 & PT 6, and I know other people are monitoring this way successfully under PT7. Any suggestions are appreciated.

Cheers,
Polaris

G5 dual 2gHz, 2gigs RAM
OS 10.4.6, PT 7.2cs1
HD with 2 Accel, 192 analog io
Magma 6 slot chassis

[Chief Technician]

Is the optical input on the 192 set to S/PDIF? I could never actually find where that setting is, but that's my only guess. I use an optical<-->S/PDIF converter for monitoring the Mac, but that's just me.

[Polaris]

Yup....its under SETUPS>HARDWARE on the right side. I think is says "use Optical S/PDIF" or something like that.

[minister]

try switching to 44.1

[Polaris]

That works for a moment then someones (either the G5's or the 192's) clock starts to drift and the vicious cycle starts all over again.

[cmaynes]

You are asking for trouble with that setup-

what does work is this-

Get a convertor that will get the optical out to AES, and go in to on of the AES pairs on the db25. It is more expensive, but on the db25 there are samplerate converters on each pair, so they will bully the mac output into proper shape- In my setup, I use a Roland digital line mixer that I have patched to digital ins 1&2. It works great.

If you use the single AES/Ebu or SPDIF ports they are clock masters, so it will be a mess unless you are wanting the mac to contro the PT clock.


charles maynes

I've run out of ideas and before I kick this G5 down a flight of stairs, I thought I would run this by the DUC to see if anyone else has experienced this problem:

We are routing the G5 optical S/PDIF into the enclosed S/PDIF on a 192 io and using an aux input to monitor the mac. When auditioning SFX (or playing iTunes or QT files etc.) we are getting garbage (anywhere from mild distortion and clicks to full scale clocking noise and muting) out of the mac. Has anyone else experienced this before? These are some of the fixes we have attempted with limited success, but the noise always returns:

Swapped optical cables
Set AudioMidi Setup to 2ch/48kHz/24bit (our sfx are 48kHz/24bit networked files).
Hooked up optical cables in both directions and tried external clocking the G5 (G5 stays locked to external).
Tossed all Digi, Coreaudio & system audio related prefs
Zapped PRAM
Reset firmware in 192 io
Tried all the various clock & pull up/down settings in PT

What's even stranger is that the noise increases with the mod level and decreases on the silences in between. I would have assumed that clocking errors would have continued. This routing was working fine under OS 10.3.9 & PT 6, and I know other people are monitoring this way successfully under PT7. Any suggestions are appreciated.

Cheers,
Polaris

G5 dual 2gHz, 2gigs RAM
OS 10.4.6, PT 7.2cs1
HD with 2 Accel, 192 analog io
Magma 6 slot chassis

[Stuart P.]

Yep, Charles is right. I do something similar to this. Go ahead and get yourself one of these, and the AES harness for the 192.

http://www.sweetwater.com/store/detail/ODL312/

I use the discontinued M-audio converter, but this should be similar.

Good luck!

[Frank Kruse]

I sometimes use this setup too but it works without problems. The thing is you HAVE to clock PT to the s/pdif optical-in of the 192 i/o. Otherwise it´s pretty normal behavior that you get clicks and pops.

frank.

[cmaynes]

Stuart-

THAT is cool.

Yep, Charles is right. I do something similar to this. Go ahead and get yourself one of these, and the AES harness for the 192.

http://www.sweetwater.com/store/detail/ODL312/

I use the discontinued M-audio converter, but this should be similar.

Good luck!

[Polaris]

Thanks all for the tips. I have it working on other G5's just fine, but if does require setting the mac audio hardware to clock to the 192 io output (which doesn't stay active without a session open so the mac goes back to internal-what a great feature!).

As a test, I ran the mac optical into a DAT deck and the same darn noise is still there...apple does have a power supply recall for this generation G5 due to clocking noise on the digital out http://docs.info.apple.com/article.html?artnum=86523 so maybe that's it.

I appreciate the suggestions and will look for a Optical-AES convertor to try.

Cheers