Digital Clock Noise...Help DIGI!!

[Rob Aubrey]

HI I had a problem with an AES/TC Electronic card on my O2R desk the other day and got in a replacement yamaha AES card. Since then I have noticed a digital clocking noise albeit at low level but nevertheless there? it seems to get louder the more tracks I have in record. The desk is the master clock and the system is Mix + on a 867 into 888/24 and Adat bridge. The 888 gets clocked through AES card as I had problems with dual clock sources running a clock to 888 via BNC socket!

I will try a few things like running an older/pre problem session on it and see if it is still there but does anybody have any suggestions aside from expensive clock sources?

ROB

[DigiTechSupt]

Originally posted by Rob Aubrey:
The 888 gets clocked through AES card as I had problems with dual clock sources running a clock to 888 via BNC socket!

<font size="2" face="Verdana, Arial">In order for Pro Tools to resolve to an AES/EBU clock, make sure that the AES output of the 02r is connected to AES Inputs 1/2 of your primary interface (ie. whichever interface is connected to your Core card).

In addition, open the Setups>Hardware window and make sure "Digital" is enabled for the Sync Mode and "AES/EBU" is selected for the ch1/2 digital format.

Brent

[vze24x2x]

Well, You really should Clock the ProTools system from the "Sync In" BNC But If you're clocking Via AES You've got to have the 888 set to Digital Input & Digital Sync. as well as have an AES signal carrying the Clocking Info plugged into AES in 1&2. That is the only input that the system will clock to.

[vze24x2x]

Don't you hate when that happens.... Brent Beat me to it

[Rob Aubrey]

Thanks for the replies.
I had been using the system flawlessly for 2 years but last week had this AES card problem and now i have replaced the card it shows a problem.

How do I clock via a BNC source (O2R or Tascam DA88) and effectively disable the duplication of the clock source from the AES card....... BUT still be able to send digital info through the AES on all channels??? I'll experiment in the meantime.

[Rob Aubrey]

bump

[Shawn Simpson]

The BNC inputs connections on the 888 are NOT word clock inputs. You can't hook anything up to those except superclock (256x) devices. Now, assuming you have no sync peripheral in the system (USD or Sync I/O), there's no reason you wouldn't be able to clock your ProTools system to an incoming AES signal. Like Brent said, make sure you've got an AES source carrying clock connected to the first AES input (1/2) of the primary interface and select your sync source to digital. On the front of the 888, you should see the sync light switch to digital and stay solid. In that situation, you should then be able to pipe in AES from the ProTools system back in to the AES inputs of the console. It doesn't really matter in theory which one is the master, as long as you're only generating clock from one source with the others set to slave to it.

I'm curious, is the 888 making the digital noise thru its own analog outputs? or is it only when you're listening to the summing buss of the desk? In general, is this a problem on the input side of ProTools or the output side?

[Rob Aubrey]

REPLY TO SHAWN

The signal going in appears clear, but the 888 output (digital via AES) is noisy, I do not use the analogue outs(UK spelling!)as the desk is digital and I do not have spare inputs or really want to impose another AD/DA process into the signal chain............having said that I will check it to see if it is clear.

I think I need to read up on this Word/super-clock business, I really thought the BNC was a WORDCLOCK in..whats the difference between word/super and the significance of 256x, I see I have that output on my MOTU midi interface,> Would I be better sourcing from that, and slaving my desk to the 888?

I had no problems before using the TC AES expansion board, perhaps it was more stable than the Yamaha version, I'll get the TC repaired and eventually it will all be sorted (I HOPE!)

ROB

[Mark Haliday]

I am not sure this is a clocking problem.

Clocking problems usually means clics and pops, not "digital noise"

Possible problems

1 - TC cards are true 24 bit.
Yamaha cards have 20 bit only I/O (a not very documented "feature"...)This means that if you don't dither from 888/24 to you are actually truncating 24 to 20.
2- TC card have a much better tolerance to clock phase problems. I lived through hell with Yamaha TDIF interfaces (with a Radar recorder) until I got TC cards and all problems vanished.

3- Earthing problem.
Bad earthing can also help digital clock signal bleeding into the audio. Try disconnecting ALL analog cabling from 02R and 888 and listen through 02R headphone output while recording digital "nothing".

good luck [img]images/icons/cool.gif[/img]

[Shawn Simpson]

One more off the wall thing to check...

Make sure your sample frequency is consistent with all the devices. Granted, a sample frequency mismatch is a bit more noticable than a low level noise, but it's something to check.

I would definitely say that if the analog outputs (checked as a reference) from the 888 are clean, the problem would definitely be in the 02R somewhere. I don't really have much experience with that desk, so I can't offer much help. Would it be possible for you to run the AES outputs of the 888 into another digital device (dat machine perhaps) to see if that will playback cleanly also?

Process of elimination, gotta love it.