Syncronisation-Coaxial S/PDIF & Optical S/PDIF

[fraz]

Hi,

I thought I'd start a new thread on a topic I've asked a lot about in the past here on Planet Z for the purpose of looking back on this later in "view your posts"-then I can find it more easily especially when everyone else starts commenting=- LOL----

The VST System link I set up (with help) was done over ADAT as the sync source-and this was reflected in the project window by ADAT modules

The other choice would have been S/PDIF and this would have had S/PDIF modules in the project window instead - but to transfer a stereo channel of audio and communication data for VST system link down a single cable it would not have been a reliable way of doing this but I've later thought I could sync over S/PDIF with VST system link but send the audio down another stereo pair to maintain the integrity of the communication data via the single cable (I've yet to try this)

The point of me writing this was some confusion on my part with Coaxial S/PDIF and optical S/PDIF which is what is being done when using VST system link-and the confusion arose because of the different modules being used in the Scope Project window eg. ADAT or S/PDIF and ticking a check box for ADAT sync made me think I wasn't using S/PDIF because I wasn't using the physical S/PDIF connection on the Scope Pro PCI card or Pulsar 2 card or Xite-1- nor was I using the S/PDIF modules in the project window

Any comments welcome - its a pointless thread in some ways as its not a trouble shoot or anything like but more of a Eureka moment for me if my thinking is correct.

Its obvious why I or anyone else could show confusion in the same circumstance and it all boils down to jargon-
Happy Christmas

[fraz]

http://en.wikipedia.org/?title=S/PDIF

http://en.wikipedia.org/wiki/RCA_connector

[djmicron]

if i remember right, when enabling optical S/PDIF, you have to use the aes/ebu module inside the project instead of the adat one, then i have not entirely understood what's your routing between the system link's pc's, because you don't need to sacrifice adat to 2 channel S/PDIF, because system link should use only 1 bit for the communication and you can share the same adat cable and channel for system link and audio at the same time and the routing must be done over asio, but i think you already done that.

[fraz]

djmicron,

My Pulsar 2 (6 dsp) & Power Sampler (3 dsp) don't have AES /EBU - They are not balanced connectors but have the RCA style phono AV connectors
My Scope Professional is balanced connectors and has AES / EBU (unless I've got it wrong)

The Xite-1 has AES / EBU for sure-My project for VST system link was made to work with ADAT but later dawned on me I could use S/PDIF just for 1 bit communication and send audio for other channels (not tried this yet)-

ADAT though uses 1 channel which leaves 7 for audio-

I think it takes a lot of knowledge and use for it to occur to you how to best use everything!-

I searched for S/PDIF on Google- and its a "standard" which encompasses coaxial RCA connectors (electrical) and Optical with TOSLINK

AES/EBU is something else again but balanced and may still be S/PDIF-

I don't want to be accused of talking rubbish (sometimes I do) but not always!-I think Gary B called AES / EBU a hotter signal than the equivalent S/PDIF connector (yellow) on PCI cards-----

[garyb]

sp/dif and aes/ebu are the exact same thing, except that aes/ebu is balanced +4 and sp/dif is unbalanced -20.
you can probably just run an adaptor and ignore the level differences, but a level matching amp(a convertor) is better. the data is exactly the same, however.

[djmicron]

djmicron,

My Pulsar 2 (6 dsp) & Power Sampler (3 dsp) don't have AES /EBU - They are not balanced connectors but have the RCA style phono AV connectors
My Scope Professional is balanced connectors and has AES / EBU (unless I've got it wrong)

The Xite-1 has AES / EBU for sure-My project for VST system link was made to work with ADAT but later dawned on me I could use S/PDIF just for 1 bit communication and send audio for other channels (not tried this yet)-

ADAT though uses 1 channel which leaves 7 for audio-

I think it takes a lot of knowledge and use for it to occur to you how to best use everything!-

I searched for S/PDIF on Google- and its a "standard" which encompasses coaxial RCA connectors (electrical) and Optical with TOSLINK

AES/EBU is something else again but balanced and may still be S/PDIF-

I don't want to be accused of talking rubbish (sometimes I do) but not always!-I think Gary B called AES / EBU a hotter signal than the equivalent S/PDIF connector (yellow) on PCI cards-----

hi, i remember i did that optical S/PDIF on my pulsar based system and had to use the aes/ebu inside the project, but if you have S/PDIF then you should use it instead, but it doesn't work over the adat modules.
Then all you need is one digital input and one digital output for system link to work, no matter if it is adat, S/PDIF, aes/ebu or whatever digital.

[fraz]

Yes djmicron,

I got the system to work with ADAT [and help from marc who did the articles for scope rise] he actually emailed me and i got there in the end.

I made lots of errors [&mis-understandings] and tried the S/PDIF but failed - I went wrong i think trying to send 2 channels of audio down s/pdif as well as communication for vst system link-

i think in time i could get that to work too but i would just use the s/pdif for vst system link and send the audio from other outputs-

which ever method is used it will "hog" or "take up" an input / output whilst it is being used for vst system link whether that is ADAT / S/PDIF / AES EBU

With the cards I've got there are plenty of options-

3 dsp pci card has S/PDIF I/O but only on one 1/8th inch jack
6 dsp pci has RCA style S/PDIF in & out
15 dsp scope pro pci card has balanced aes / ebu for the same

there are the adat options as well on the cards - so lots of options etc.....which is good but it takes time to understand there are options and more than one way of achieving the same thing - that justifies my decision years ago to get the cards i've got eventhough they were way above my head at that time -

[Steve Fogal]

Yes djmicron,


I made lots of errors [&mis-understandings] and tried the S/PDIF but failed - I went wrong i think trying to send 2 channels of audio down s/pdif as well as communication for vst system link-

i think in time i could get that to work too but i would just use the s/pdif for vst system link and send the audio from other outputs-

which ever method is used it will "hog" or "take up" an input / output whilst it is being used for vst system link whether that is ADAT / S/PDIF / AES EBU

I run 3 PC's with a coxial s/pdif connection in a VSL 'ring' network just fine...running the VSL data, sync and stereo audio. I don't have the need to send any midi via the VSL network, instead I prefer to record all my midi tracks directly into my dedicated VSTi machines. All my PC's and audio interfaces are the same spec for compatibility. I don't need to send separate audio feeds via various other types of I/O I have available. I only send a stereo audio sub-mix among machines through the VSL network.

Just a chime in late here in case anyone else is interested in VST System Link. There's a few things that can be done wrong along the way setting VSL up. I made the same mistakes over and when it wasn't working, it was because I connected it wrong. Too much to go over about what can be wrong, but what finally helped was reading the pdf's over & over. The manual is vague, so I did a lot of experimenting to get things right. One of which was I was sending & receiving on channels 9/10 for the in/out on the s/pdif in the VSL dialog box, when all along I should have been using ONE channel ....channel '9' (or channel '10') for the VSL I/O over s/pdif. The other thing I did wrong when setting up was the I/O routing on my sound card.

[fraz]

Hi Steve,

Yes I made the mistake of sending a stereo audio channel down the SPDIF along with the communication data for vst system link.

I did get it working after help understanding it from people here on the forum-and I used ADAT with one channel for communication, leaving another 7 channels for audio.

A thought occured to me months later [as is often the case]- that I could send communication for the VST system link via SPDIF [like you've done] and send audio from somewhere else and it also occured to me I wouldn't need to send any audio at all from one machine to another if I didn't want or need to.

Our equipment has alot of capabilities and options which take a long time to understand---------Its great you've done this too.

[Steve Fogal]

I didn't think I'd get a response so quickly, or not at all on a past thread I was actually looking up System Link stuff on the internet to satisfy my obsession with it, that's how I found this forum.

Right, audio doesn't even have to be passed on through one computer to the next if that is your preference. I know some run all their machines audio into a mixing desk and monitor everything from there. Their outputs (digital or analog) can be merged into just a stereo track of 'any' recording medium when mixing down.

There's so many more possibilities than one would 1st realize with System Link, you can really do things the way you want with using your own creativity... For the time being, I have the 'ring network' via s/pdif for VSL's data, sync and stereo audio, which does the trick for me. It was an additional hurdle at 1st trying to route & pass audio through one machine to the next etc, but got it going well.

I also get new thoughts & ideas as I go, and that's a good thing! Although I currently have my 3 PC's in the 'RING' network, I have this idea....and I've only just have began to experiment with this... I found out that you don't really HAVE to complete the VSL 'RING' Network at all, and sending your choice of a digital signal out with VSL sync/data works in only ONE direct too. That is, I can tie all 3 of my PC's (via s/pdif in my case) from PC-1 to PC-2 and to PC-3 (and not complete it back to PC-1 again). In this particular case, by pressing play/stop etc on PC-1, PC's 2 & 3 follow. If I press play etc on PC-2, only PC 3 will follow... PC-1 will not follow of course, because the 'ring' is not completed back to PC-1 on purpose.

The above brings to mind that if desired, just one master PC ican be used for the actual transport & sync, and if the 1st original digital signal from there is properly split up/replicated, it can be simultaneously distributed among any number of VSL slave machines. That is, the 'point' of this is that all slaves will receive the VSL signal at the exact same time, where as in the traditional 'ring' network, they're actually in succession. As small as this really is, there is some amount of latency/lag time in reaction to transport control. How then one chooses to pass audio (or not) is another set of options.

I've also found that 3 PC's in the traditional 'ring' network isn't as bad as I thought by what I've read with added latencies involved....some saying 2 PC's is ok, but 3 or more get's problematic, so far not in my case...even with sending VSL data & audio together on the same s/pdif (and I tested with a few midi tracks added as well), the lag & audio latency is so small, I can't tell until I align audio up from previous machines to the grid of the 1st machine, and see that they're only slightly off on the grid. I can't hear any latency if I'm using all 'different' audio tracks, midi tracks, etc...the only way I can actually hear anything, is if I copy & paste an exact same audio.wav file to all machines, then play...in which I'll hear a slight flange effect...but in reality I'll never do this copying in a real song project among machines. But 'knowing' the audio is off on the grid (when in a ring network), they can be offset or nudged. Of course one can send audio via separate individual feeds back from all slaves into the 1st master PC (or mixer) so that all audio will be received at the exact same time frame, as often suggested in larger VSL networks. And I'd that think this would be far more important in than just the idea of sending in a separate feed, other than the same one with the VSL data & sync.

I have adat capability too, but have not used it for VSL, but it's more possibilities to consider with.

[Steve Fogal]

Slight update to add. After my last post a while back, I got to thinking more about creative ways of routing for larger VSL networks, and further consideration of not running it in a traditional 'ring' network, and more about having one computer feeding into a digital distribution amp, to all other computers. I found a solution...

I recently purchased an 8X8 matrix switcher/distribution ampunit, which has coaxial s/pdif connections (8 in/8 out). I run all my computers sounds cards s/pdif I/O's to and from my matrix switchers I/O's. Any ONE computer of my choosing, at any time, can effectively be the master, sending the VSL data into the matrix switcher, which then can 'simultaneously distribute' that VSL data to one or more of the matrix switchers outputs, to all connected computers... ALL computers RECEIVE the VSL data simultaneously. With this 8X8 matrix, up to 8 computers can be connected (even more if using say a 16X16 matrix switcher).

On one hand, the traditional 'ring' network is handy for VSL, because it gives flexibility to allow any one machine, to control the transports of any other, at any time...along with VSL data & audio....nice with multiple/simultaneous users. But you also will be running everything in a loop, IN and OUT of all connected computers, and that can add up latency, but in my experience it's relatively negligible with even 3 computers anyway. With a matrix switcher, in my case of just ONE person working alone, I can press a few buttons and route the digital s/pdif audio and/or data in any configuration I wish, with any number of computers I want to use, at any given time.

The matrix switcher for me personally, is a far better solution when using multiple computers. Another major BENEFIT of a matrix over the ring network, is to be able to have any computer within your network OFF-LINE, which will break the VSL network at that point, so you would have to physically reroute your cables to compensate. And unexpectedly, I found that by not being in a 'ring' network, and using a distribution method (1 in, up to 8 out) VSL has proven to be much more stable. Previously, VSL would get disconnected after a while (several minutes to an hour), and it was at random. With the matrix distribution switcher method, I've not got disconnected so far at all in the couple of months I've had it in use. I'm thinking it has something to do with the ring, somehow coming back into itself...because before the matrix, for a test, I'd disconnect the last return (either by the physical s/pdif cable, or by way of internal sound card routing), effectively cutting off the true 'ring' which it would always be stable too. This then became my work-around. But that was a hassle IMO, plus I had the idea that I wanted the all the effective slaves to 'simultaneously receive' the VSL date from the effective master. This has worked out extremely well.

A convoluted system maybe, but I plan to further extend this system, and explore the limits.

And just to be clear, in my experience of sending VSL data AND audio down the same s/pdif cables, I've not had any problems with it. You can always route audio separately as has been said. I'm only just taking stereo audio sub-feeds from each computer along with the VSL data..not a problem.

[m.my91]

hello
i resolve a spdif to aes/ebu impedance converter with a pulsar 2 spdif and protools 192 aes/ebu.
i use this:
http://www.scientificonversion.com/catalog.html
you can plug aes xlr to spdif (2 plugs on xlr, sc936 or sc937).
it coast 20 euros and it work very well at every samplerate (32 to 96 khz).
thanks

[Steve Fogal]

An update after a couple of years...

Still working with VST System Link, and using my s/pdif matrix switcher with it. I've extended my System Link network, and have tested this with 5 desktop PC's, and a laptop. All in perfect synchronization!

[dawman]

Excellent news.
Show us some stuff.