Word-Clock Technique

aquaman

aquaman

New member
I am going to be purchasing a new AD/DA with word-clock in the near future, probably either Apogee Rosetta 200 or RME Fireface 400. Both of these units have word-clock I/O for syncing other devices.

If I want to use the interface as the clock source for my music software can I just run the S/PDIF out of the interface and go to my current soundcard, M-Audio Audiophile? Or do I have to actually use the word-clock out and run it to the word-clock input of a soundcard like the M-Audio Delta 1010? If the latter, are there any other soundcards with word-clock in other than the M-Audio Delta 1010, because I can't seem to find any?

Many thanks.
 
Right... What MS said.

Run the spidf from the Rosetta to the M-Audio card.
Set the M-Audio card (via the software applet) from sync internal to sync external from the spdif and your good to go.

A heads up... Even though the Deltas have a word clock connection, they dont work good. All 3 of my Delta 1010 units (bought in different years I might add) had to go back to M-Audio for an upgrade to "fix" a problem with the word clock input where a small amount of the clock ocillations(or some kind of noise) migrate into the audio.
Sounds pretty bad .
Without the fix it sounds better syncing all via spdif.
 
Thanks for the info. Does firewire carry wordclock also? If so I could just bypass the old Audiophile altogether (if I get the RME; the firewire card for the Rosetta is pretty steep).
Thanks
 
I am not sure which format of sync it carries, but I would imagine the firewire would have to carry some sort of clock signal either sepreately or imbedded in the audio.

I am not much the tech geek, I hope someone else chimes in.
 
tmix said:
I am not sure which format of sync it carries, but I would imagine the firewire would have to carry some sort of clock signal either sepreately or imbedded in the audio.
Click to expand...

No, not really. FireWire audio data is just data.

Clock signals are a continual stream of pulses, and at the start of each pulse, the ADC or DAC converts a single sample of sound to data or vice versa. It only makes sense in the near-analog domain, i.e. before the data is sent across a computer communication bus like FireWire, USB, or PCi.

The exceptions to the rule are S/PDIF, AES/EBU, and ADAT lightpipe. Those busses are clocked so that they can be used to easily share devices between tape decks or converters and still allow the receiving converter's inputs to work.

FireWire, though, like most computer-based busses, doesn't attempt to do that. The performance requirements of receiving such a stream (without receiving it in hardware) raw would be really intense. The computer would have to drop whatever it was doing and service the device too frequently. Because of the overhead involved, it isn't really practical to receive S/PDIF or other such streams with a computer directly unless you use intermediate hardware to do the decoding of the stram and temporarily store and retransmit it to the computer in larger chunks of data.

Thus, FireWire and USB transfer data in discrete chunks of many samples at a time, called packets. The fewer chunks per second, the higher the latency, but the lower the CPU overhead. PCI does something similar with a ring buffer, which the device driver scans periodically, reading out several samples at a time whenever it does.
 
That makes sense.
So I guess if any clock was needed for sync of interface to say a digital mixer etc, it would be done at the convertor box prior to data streaming.
 
Just getting back to this. If firewire (and probably USB so I am not sure how my current M-Audio card will work) do not carry clock signals, how do I sync my sequencer software to the clock source? For example, in Cubase's device setup menu for a project, you can specify the clock source to be internal or external. My main interest in getting an interface with word clock is not to sync up various hardware but to use it as the clock source for my host sequencer program. What kind of physical interface do I need to achieve this. I know the M-Audio Delta 1010 works but has a MCI card to interface with the computer.
Thanks
 
If you don't have a data stream present at the digital input or word clock input of your interface, your software (and interface) will default to "internal". If you do have an outside clock source at the digital input or word clock input, you still have to specify that the interface sync to that external input. *Any* interface that you buy will have it's own internal clock, it has to in order to function properly.

So, based on your earlier question regarding the Apogee 200, you'd run the SPDIF output of the Apogee to the SPDIF input of the soundcard, and then specify the SPDIF input as the clock source in the software.
 
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