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wiz1der

SPDIF Patch bay?
« on: May 12, 2005, 06:59:49 PM »
I got this crazy idea for a half rack  12-16 points for all my ins and outs of spdif.


Is this as simple as a half rack box and some female RCA jacks? Of course I wll be using 75 ohm video rca for patching but is there more to it than that?

And also, Can I put a splitter on a SPDIF connection without degrading quality?


clintrubber

SPDIF Patch bay?
« Reply #1 on: May 12, 2005, 07:27:20 PM »
I've been lusting for such a thing as well but didn't jump yet. Point is, there are a few different tastes out these: S/PDIF as coax(RCA) and as optical(toslink), AES/EBU on XLR-3 etc. Would one 'style' suit all your gear ? If not then you have to provide several of each and hope you don't run out of one taste too soon.

There's also a cheap Fostex-box, but I didn't buy since it had mostly optical, which I don't have much.



http://www.americanmusical.com/manuals/fostex/fosds8_servicemanual.pdf
http://www.fostex.com/support/pdf/fostex/ds8/ds8_white_paper.pdf

There are schematics inside, but I understand you want to keep everything passive, right ? I think your original plan can work - I even bought a simple 3-tapedeck-audio-switcher (all passive, so just switches & RCA-connectors) for that purpose once but haven't really tried it.

The multing of those signals doesn't sound like a good idea though, but it may work. point is, it'll be hard to tell when exactly you begin to notice the influence (jitter resulting in... etc) so I wouldn't make it too spectacular there.

Quote
but is there more to it than that?

You should check you're not messing up the ground connections and don't make the total cable-length too long. S/PDIF was not meant for really long lines, just the order of magnitude of a meter, I thought. I guess it'll just work (function) for much longer distances though.

Bye,

  Peter

gyraf

SPDIF Patch bay?
« Reply #2 on: May 13, 2005, 05:40:08 AM »
In our studio, we use BNC connectors for S/Pdif patchbay. Good connections, HF proof, easy to get good cables. We use simple RG58 cable for S/Pdif cabling - works well up to some 20 meters.

Jakob E.
..note to self: don't let Harman run your company..

smorphet

Re: SPDIF Patch bay?
« Reply #3 on: May 13, 2005, 09:25:35 AM »
Quote from: "wiz1der"
I got this crazy idea for a half rack  12-16 points for all my ins and outs of spdif.

Is this as simple as a half rack box and some female RCA jacks? Of course I wll be using 75 ohm video rca for patching but is there more to it than that?


I've just done a simple panel with four outs and four ins.  It works fine.  It's just eight bulkhead mounting 75 ohm BNC socket-socket connectors on a panel.

Digital signals are quite robust, but they have the disadvantage of working perfectly right up to the point where they stop working altogether.  That is,  a cable with n dodgy joints will work fine, but with n+1 joints it won't.  Therefore, it's sensible to minimise the number of joints, and maximise their quality.  The BNC bulkhead connectors that I chose mean no internal wiring in the patchbay, and BNC helps to maintain constant impedance better than RCA so it should do a better job of preserving the signal integrity.

You need to select your cables carefully.  For the fixed wiring just about any 75 ohm coax will do.  For the patch leads it needs to be robust and flexible.  Many 75 ohm coaxes seem to be solid core, which I think would break quickly in use.  I found some stranded video coax from Van-Damme which seems to work OK.  Take care when twisting a tight RCA in or out, as this will put strain on the cable.  BNC is better, with its bayonet lock.

Quote

And also, Can I put a splitter on a SPDIF connection without degrading quality?


Not something I've ever tried.  I wouldn't make a habit of it.  But, provided the total signal degradation is below the invisible threshold, it'll probably work.  The "correct" way to split SPDIF would be with a video distribution amp or similar.

Steve.

adrianh

SPDIF Patch bay?
« Reply #4 on: May 13, 2005, 01:24:23 PM »
4 words

video patch bays
AES3ID

***************
Use 75 ohm video (WECO) style patch bays just like
the television guys have used for 30 years.

Use a balun to make all AES3 signals into a coax.

Use very good 75 ohm high speed coax like Belden 1505 (A) or (F).

Look up the AES3ID spec.

This "Rane Note"  is very good
http://www.rane.com/pdf/note149.pdf

Yes SPDIF will most likely work stright into
the patch bay.

BYacey

    Where dogs wear thermal underwear, Alberta, Canada
  • Posts: 739
SPDIF Patch bay?
« Reply #5 on: May 13, 2005, 01:32:53 PM »
I would like to build a patchpay for toslink. Anybody know where to source toslink female to female bulkhead couplers?  I want to bring up my adat recorders toslink in and out connectors on a rack panel.
Bill Yacey
"Adjust R116 for least smoke"

adrianh

SPDIF Patch bay?
« Reply #6 on: May 13, 2005, 04:37:44 PM »
Bill;
Digi-Key in the past had them.
Look on the catalog page with the plastic bulk fiber.
It is an AMP (Tyco) product.

If you cannot find them send me a note.


 

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