Topic: Word clock question...

[Genghis Cougar Mellen Khan]

Theoretical question:

You have a unit that is suppose to be bit-accurate and another that can accept a WC, if you're sending one unit the digital out from a V3 and the other linked to the WC out, the 2 sources should share the same identical clock? 

I guess what I'm wondering is... is the timecode information inherently part of the data stream or does it go beyond that? 

I would like to be able to run 4 channels and not have to deal with sync issues in post, not really interested in an R4 at the moment.

[Brian Skalinder]

You have a unit that is suppose to be bit-accurate and another that can accept a WC, if you're sending one unit the digital out from a V3 and the other linked to the WC out, the 2 sources should share the same identical clock?

That's my understanding.  My ultimate 4-ch goal is a V3 + bit-bucket + 722.  Some day.

Hopefully someone with more knowledge and first-hand experience on this one will chime in.

[Genghis Cougar Mellen Khan]

You have a unit that is suppose to be bit-accurate and another that can accept a WC, if you're sending one unit the digital out from a V3 and the other linked to the WC out, the 2 sources should share the same identical clock?

That's my understanding.  My ultimate 4-ch goal is a V3 + bit-bucket + 722.  Some day.

Hopefully someone with more knowledge and first-hand experience on this one will chime in.

I was thinking of some possibilities...

Getting the ACM mod for my 671 and picking up a stock HD-P2 for the 2nd set of channels.

or

Getting a 722 and leaving my 671 stock and use it as the bit bucket.

[Brian Skalinder]

Getting the ACM mod for my 671 and picking up a stock HD-P2 for the 2nd set of channels.

I see a WC input on the HD-P2, but not an in or out on the 671...not sure how you'd sync the two.  Am I missing something?  Or are you looking at V3 > 671 and V3 WC-out > HD-P2?

Forgot about the P2, I could use that instead of the 722 for a significant chunk less cash.

[Genghis Cougar Mellen Khan]

I see a WC input on the HD-P2, but not an in or out on the 671...not sure how you'd sync the two.  Am I missing something?  Or are you looking at V3 > 671 and V3 WC-out > HD-P2?

I was thinking:

You're correct, the 671 has no WC input, I'd be using the V3 as the master clock (WC to the P2) and the 671 as a bit-bucket.

[BC]

Or are you looking at V3 > 671 and V3 WC-out > HD-P2?

Does that mean you would need to run WC and analog outs from the V3 to P2?

[Brian Skalinder]

Or are you looking at V3 > 671 and V3 WC-out > HD-P2?

Does that mean you would need to run WC and analog outs from the V3 to P2?

For 4-ch, I'd expect to run it like so:

Mics1-2 > V3 > digi-out > bit-bucket
Mics3-4 > HD-P2 + V3 > WC out > HD-P2

[Brian Skalinder]

in the above setup you end up with two separate, two channel recordings that are both synced to the same clock?  then one can blend mics 1/2 with mics 3/4 to taste in post easily and effortlessly since there is no need to sync?

Basically, yes.  There may be need for an initial sync, though.  For example, if one set of mics is on-stage and the other in the AUD, one set of mics will have a delay relative to the other.  Or if 2-ch are AUD and 2-ch are SBD, the AUD mics may have a delay relative to the SBD.  But after performing the initial sync, no further syncing is required because there's no clock drift.  So - align once, and done.  No re-aligning every 2-3-5-however many minutes as the clocks drift.

[TNJazz]

Theoretical question:

You have a unit that is suppose to be bit-accurate and another that can accept a WC, if you're sending one unit the digital out from a V3 and the other linked to the WC out, the 2 sources should share the same identical clock? 

I guess what I'm wondering is... is the timecode information inherently part of the data stream or does it go beyond that? 

I would like to be able to run 4 channels and not have to deal with sync issues in post, not really interested in an R4 at the moment.

In theory, yes they share the same clock.

Unfortunately, the two sources may still not line up properly in post.  There must be other reasons for sync drift.

I know because I tried this recently with my Rosendahl providing clock to 5 different devices (24 ch multitrack and a 4 channel aud/sbd backup).  The clock signal was sent to 3 digital preamps and my Alesis HD24 for the multitrack, and also to a Metric Halo for the 4 channel backup.  In post, I was unable to align the 24 channel mix with the 4 channel backup, even though ALL common clock was generated by the Rosendahl.

You may get lucky; you may not.  I have not tried since then but I will probably do something similar at the next gig I have because this thread has piqued my curiosity again.

Dirk

[Roving Sign]

My experiment using the same clock on two A/Ds also failed...(however there was digi-noise in one recording (cell phone -- I assume))  - not sure if that could have affected the post-sync...

Is it possible the recording device is "re-clocking" the signal as it comes in?

I know high-end audio guys always talk about "re-clocking" - - is there such a thing?

[JasonSobel]

Is it possible the recording device is "re-clocking" the signal as it comes in?

I know high-end audio guys always talk about "re-clocking" - - is there such a thing?

yes, there is such a thing as "re-clocking" and that could be what is going on in both of the examples above.

with the Tascam HD-P2 (for example), there are menu options to specify the audio source (mic in, line in, or S/PDIF), and you also need to specify the clock source (internal, S/PDIF, or Word Clock)... to continue this example, if you send the HD-P2 a S/PDIF signal, but have the clock source set to internal, it'll re-clock the incoming data based on it's internal clock.  so, if using the HD-P2 to sync up with another A/D, it's important to choose the WC option for the clock source.

in both examples above, the actual gear used wasn't specified, so it's hard to know exactly why their was drift between the sources.  if the two recordings were using the same clock, that wouldn't have happened, so my suspicion is that some of the recording gear was re-clocking the signal...

[TNJazz]

if the two recordings were using the same clock, that wouldn't have happened, so my suspicion is that some of the recording gear was re-clocking the signal...

It did happen, unfortunately.  My setup was as follows:

3x digital preamps (Focusrite, Ramsa and Mackie Onyx) all slaved to word clock input
all running ADAT to an Alesis HD24, ALSO slaved to word clock input
plus
Metric Halo 2882 ALSO slaved to word clock input going to a Powerbook G4 via firewire (4ch backup)

All 5 clocked devices were sent clock signal from the Rosendahl (which has 12 WC outputs, so it's not a daisy chain or distribution amp thing)

[Roving Sign]

My set up used a dbx386 (pre/a>d combo) as the master clock...dbx clock out to a Behringer Ultramatch A/D - (via BNC)

The 386 used a CO2 to convert coax to fiber and fed a JB3

The Behringer has optical out - feeding a second JB3

Pretty sure I had all the switches in the proper place...

I was going to do some cassette transfers later today - maybe I'll set up this stuff again - give it another shot...

[terrapinj]

You have a unit that is suppose to be bit-accurate and another that can accept a WC, if you're sending one unit the digital out from a V3 and the other linked to the WC out, the 2 sources should share the same identical clock?

That's my understanding.  My ultimate 4-ch goal is a V3 + bit-bucket + 722.  Some day.

Hopefully someone with more knowledge and first-hand experience on this one will chime in.

why not 744 + pre? seems you'd be close to the same $ by time you figure in the v3 and bit bucket and would be much easier and smaller to run

[ethan]

I've got two working AD1K's now and am planning on doing some 4 channel stuff by syncing them.

-e