Clocking Question for Mobile Rigs

[machinefunk]

Hello,
We are about to embark on a 48 track live recording using the following rig:

6 X Presonus Digimax 96 Preamps -> ADAT Litepipe-> 2 X Alesis HD 24 Hard Disk recorders

After doing a production rehearsal this weekend we heard some digital noise in playback. Upon further review we found that the first 8 tracks are fine and that the problem was intermittent thruout the other 40. We came to the conclusion that this must be a clocking issue.

So my question:
Has anyone clocked multiple Digimax preamps together before?
I am wondering if its worth it to sync these or go with an external clock and sync everything to that. Any help is appreciated.

thanks,
Matt

[Rusty Cage]

You definitely need to run them in sync. What you need is wordclock distribution.

Lucid have a 6-way distributor that would fit your requirement nicely... I don't really know of any others.

[DeadPoet]

I have no experience with the presonus units but have a HD24.

bought a clock cheap (Mutec Smart Clock) which has several WC outs to distribute WC to my HD24, a Behringer ADA8000 and an RME adat card.

I haven't used the Behringer unit much live yet, but have experienced random digital spikes at least once when i used it - only in the 8 channels coming from the Behringer, NOT on the other 16 channels coming from 16 preamps.

The spikes were easily removed but quite a pain in the butt to do so.



edit: i just checked the digimax specs, it has analog outs on every channel, right ? why not save you the trouble of going A/D and having to it clock the right way and let the HD24 do the A/D-ing.
If you insist on using WC, it has WC out as well as in. buy a WC distributor (Mutec has one as well as many other companies) and dedicate one of the units to be master...

Hope this helps,
Herwig

[Sofa King]

Originally posted by machinefunk
Hello,
We are about to embark on a 48 track live recording using the following rig:

6 X Presonus Digimax 96 Preamps -> ADAT Litepipe-> 2 X Alesis HD 24 Hard Disk recorders

After doing a production rehearsal this weekend we heard some digital noise in playback. Upon further review we found that the first 8 tracks are fine and that the problem was intermittent thruout the other 40. We came to the conclusion that this must be a clocking issue.
t

Hi,

Although I'm only slightly familiar with the Presonus pieces, and Alesis recorders, I do a bit of location digital recording, and here’s some stuff to check, and some stuff that has worked for me.

I’m assuming you're coming in at 44.1 or 48 kHz.
and all of your master /slave scenarios are correct.

also, I not sure how you are linking/slaving the 2 recorders together, that could be causing some issues.


Id recommend Apogees Big Ben, it has 6 outs, and has worked nicely on my gigs.
I rent mine from the folks at Black Bird in Nashville.

Something to definitely check, is the quality/length on the litepipe cables.

I had some random clocking rash on a recent date.
96 tracks, two dif formats, digital consoles, video.
I was blaming the problem everything, and here the problem was too long of litepipe cables.

Since, I've switched all my stuff to AES 110ohm.

Oh, and I strongly disagree with the other poster. I would not convert at the Alesis units.

Best
Sean

[Waylon]

or, for yet another opinion, just daisy chain the wordclock form the first preamp to the others and then to the ADATs...


if it uses BNC connectors, get BNC "T" connectors to do this, and you can keep it from being too long a trip form the first to last device. Should work fine.

[Waylon]

did you get your clocking problem sorted?? what method worked best?