192 I/O realtime sample rate conversion?

[Simon R.]

OK, I understand that the digital ins of the I/O 192 can realtime convert sample rate of the incoming signal. As it says in the manual, you can stream 44.1khz into the ADAT into a 96khz session.

What I DON'T understand is, how can this ever work in reality? Don't I need both the I/O 192 and all other digital sample sources clocked to the same sample rate with the same clock to avoid problems? Say... if I have Logic Studio running on one machine at 44.1khz but want to record this to ProTools on another machine, recording into the 192 I/O. Shouldn't it be impossible to run a 96khz session there at the same time as running 44.1khz on the Logic machine?

[O.G. Killa]

weird, I agree. but it does. I just loaded a bunch of tracks off a 48KHz/24bit dat into a 96KHz/24bit protools session through AES. Worked seamlessly and in realtime. Makes the 192IO totally worth the price!

[Simon R.]

Originally Posted by O.G. Killa

weird, I agree. but it does. I just loaded a bunch of tracks off a 48KHz/24bit dat into a 96KHz/24bit protools session through AES. Worked seamlessly and in realtime. Makes the 192IO totally worth the price!

OK but how was the DAT clocked and how is ProTools? I haven't experimented with this myself because I am just about to buy a HD system - just planning ahead what I can do.

[Eric Seaberg]

That's what SRC does. The 192 is referenced to your session sample rate and the input takes in whatever you send it, and re-clocks it to the session rate. No black-magic, that's what Sample Rate Conversion is supposed to do.

Granted, you'll have less jitter if everything is clocked to the same SR, but when you've got audio with different rates, there's no other way around it.

Just make sure you turn SRC OFF on the 192 I/O when you don't need it.

[Simon R.]

Thanks, Eric.

I still don't understand how I should clock things. Obviously, I need my Logic setup + the slave machines that I run along it clocked at 44.1khz when I use it. So, let's say I provide 44.1khz via word clock from a clock gen to those machines. What should I do to the Pro Tools machine/192 I/O - provide the same word clock? And Pro Tools will accept that I run a 96khz session while the word clock tells it's running 44.1khz on the word clock input?

[Tweakhead]

Several units can perform this function. My personal favorite is this:
http://www.brainstormtime.com/dcd8.php

[Simon R.]

Still haven't gotten a really clear answer I think:) So.. do I need something like the DCD-8 to be able to run 44.1khz into a 96khz project in Pro Tools?

[Eric Seaberg]

Originally Posted by Simon R.

Thanks, Eric.

I still don't understand how I should clock things. Obviously, I need my Logic setup + the slave machines that I run along it clocked at 44.1khz when I use it. So, let's say I provide 44.1khz via word clock from a clock gen to those machines. What should I do to the Pro Tools machine/192 I/O - provide the same word clock? And Pro Tools will accept that I run a 96khz session while the word clock tells it's running 44.1khz on the word clock input?

If you want to run a 96k session on ProTools, then you need 96k wordclock. Since you don't have that, or so it seems, just keep all your other gear locked to the 44.1k clock as it is, run ProTools INTERNAL 96k and turn on the SRC for those inputs.

BTW, we do have a DCD-8 in our HD truck which drives 128-I/O of ProTools and our SSL at 48k, and all of the CDRs and backup systems at 44.1k, all referenced to video blackburst. It works great, but isn't really necessary in your situation.

[spicemix]

I think it will "just work" because the SRC is allowing the 192io to run at multiple clocks at once. Nothing more needed. It's a resampler...

Speaking of which, not all resamplers are of the same, or even adequate, quality. I don't see the 192i/o realtime SRC plotted here, and would love it if someone capable would submit test results for it:

http://src.infinitewave.ca/

[O.G. Killa]

Originally Posted by Simon R.

OK but how was the DAT clocked and how is ProTools? I haven't experimented with this myself because I am just about to buy a HD system - just planning ahead what I can do.

Dat set to it's internal clock. Protools set to it's internal clock.