Wordclocking/BNC cable and setup

[theslingerland]

Again I'm seeking advice from this awesome forum!!

I'm not up to speed on Wordclocking - I don't fully understand what it is, how it functions and how critical
It all is - so:

1 can someone explain in laymans terms what it is?
2 I have a UA 4710d with a focusrite 428 running into into it - I'm using the ADAT out into a MOTO 828 mk2 into
My mac. I also have a Focurite octopre that's going into the 828 on line inputs. The 828, 4710d and Octopre all have Wordclocking I/o - which do I connect to what, where, why...?!
3. Finally - it looks like I could spend between £1 and £100 on a BNC cable - which is the best cheap option and What is the spec/item details that I need to check for?

Sorry for all the questions - this forum has saved me do many times....!!

[theslingerland]

Anything on this would be helpful - actually the more I research this topic, the more I feel a little lost by it all. I get the feeling it's going to be one of those things that I will end up spending more time looking into and not enough time playing/recording.....!

[PhilDW]

Here's my non-technical (and probably dumb) take on it. If you were recording with several different A/D converters going into one (say PCIe) card on your computer, and maybe monitoring from a D/A converter too, you kind of want them to all get their marching orders (the clock) from one place to keep them all lined up. So you could think about a standalone clock to drive them all. It is also said that some external clocks have characteristics (such as reduced jitter) that improve sampling and conversion resulting in higher quality.

Jitter explained - Part 1.3 [English]

If you have one A/D converter like your UA going into that PCIe card you don't really need an external clock, but both will probably have a clock source, and both are likely to have the equivalent of a setting that says "use the clock from the other end" and you'd choose the better clock. Or if you know that an external clock would improve quality you'd slave them both to a separate clock.

[theslingerland]

Thanks for the reply - so with my set up - are you saying I don't need to worry about connecting all of my gear being hooked up?

[oretez]

at some point the kind of daisy chain of devices you seem to be describing -- Foscusrite ISA428 to UA4710d to MOTU 828 MKII -- starts to have performance issues, but theoretically you have clock sync between the UA & Foscurite resolving as a single clock source which is then sync'd to 828 MkII via the ADAT port and my guess is that you need to use the 828 as the clock source on this simply to sidestep any issues with the analog signals . . . all these 16 analog channels are passed via firewire to computer w/o additional clock headaches . . . probably.

Unfortunately daisy chaining word clock is no better (no less like to produce issues) then daisy chaining multichannel digital audio. In your set up I don't think word clock would provide any assistance. Just more cables to sort out. If for example the 828 had two work clock out connectors you could sync the UA & Foscurite independently to the 828 and this might be a marginally more stable setup. If the device you felt had the most stable clock had ability to distribute, as opposed to daisy chain, clock signal to each A/D this would also produce the more stable hook up.

But my gut response, based on some experience connecting multiple A/D sources to an 828, is that Word Clock is probably not required.

As far as cables any marginally reputable 75 ohm coax cable will be fine. Years ago I bought about 100 ft. of standard cable TV cable for about $10, haven't used it all and have not had difficulty with it distributing clock.

good luck

[theslingerland]

Well the 428 is going into the 4710d on line ins, not digitally - so the only two bits of kit that are digitally connected are the 4710d and 828 via ADAT light pipe - is it worth me clocking those two to each other? If so, which way around would be best?

[theslingerland]

Any clues whether there's any benefit to me hooking up the 4710d to the MOTU 828 or is there any benefit to me hooking up any of the gear that's not connected digitally at all?

[oretez]

Originally Posted by theslingerland

Well the 428 is going into the 4710d on line ins, not digitally - so the only two bits of kit that are digitally connected are the 4710d and 828 via ADAT light pipe - is it worth me clocking those two to each other? If so, which way around would be best?

They are 'clock sync'd' via the ADAT (lightpipe)

The only point to using word clock in your description of you signal path would be if one Clock (the 428 for example) were demonstrably vastly superior then you would need a clock distribution system (not daisy chain)

unsync'd a/d's trying to work in tandem is not a subtle situation . . . it is unlikely that you will not know that devices are not cooperating

so again the benefit, such as it is, to distributing word clock (in your setup) would only be if one clock was vastly superior to the others. And clock distribution adds a layer of complexity to troubleshooting (& at some point when tying a bunch of disparate digital devices together troubleshooting is inevitable) that must be considered in addition the cost of a super clock distribution strategy.