[sdiy] More of that S/PDIF stuff.

[Magnus Danielson]

From: "Batz Goodfortune" <batzman at all-electric.com>
Subject: [sdiy] More of that S/PDIF stuff.
Date: Fri, 03 May 2002 02:23:43 +0930

> Y-ellow Ya'll.
>          Well apart from the fact that the glorious Yamaha O1V and it's 
> podule doesn't do what the guy who sold it to me said it would. And apart 
> from the fact that it seems Humpty has once again struck down some of my 
> most precious data in the guise of doing me a favor. The S/PDIF thing 
> works! So thank you all for your input. If only you guys wrote operating 
> systems the whole world would be saved from tyranny.

But some of us do! Didn't you know? :-o

> I thank you greatly and this time I even left my pants on while doing it.

Good for you, and the neighborhood!

> However. Apart from an order of magnitude jump on the Schodinger scale of 
> logistical nightmares, it would now seem I have a potentially new problem. 
> Possibly an unsolvable one. (Or was that his cat that came up with the 
> scale as pay back for Schrodinger having locked him in the box in the first 
> place?)

I don't know, but that cat made a great rug for me... keeps my hair
stand out!

> Anyway, the route question goes a little like this. "How messed up do you 
> think the S/PDIF signal would become if I tried to drive multiple inputs 
> from a single output?" Now I know in video, you get a bit of a signal loss 
> but nothing the receiving end can't handle. [USUALLY] But there is no kind 
> of AGC in an S/PDIF or AES/EBU receiver is there?

I think that you normally is without a real AGC (which would be the
propper way) but rather sit there with a diff-amp and amplify way.

You could split like you say, but it is not nice. It is not big magic
involved in building a buffering system which splits the signal for you.

> It might come down to trying to distribute synch through the mixer from a 
> single source. And then on to S/PDIF inputs of which I hadn't planned on 
> actually using. And even then, I have to hope that every device will oblige 
> me by accepting it's master sync from an input that isn't actually in use.

Well, it better follow AES 11 or you might consider yourself screwed! ;O)

> It would mean that I would have to distribute some sync from digital 
> outputs I don't have. It would also mean that I would also have to clock 
> the master through the desk and distribute it from there because in some 
> cases I actually WOULD need to use the inputs as actual inputs and... Well 
> you get the picture. And all this assumes that everything would accept 
> this. I already know of one that won't.

Take a peek at the Crystal Semiconductor CS8420, eats AES/EBU (or
S/P-DIF), spits out AES/EBU (or S/P-DIF) but will samplerate convert
for you if you beg only slightly. Interesting little device. You
*where* asking for cheap TBCs, wheren't you?

> Oh but it gets even better. I'd have to derive the master sync from an 
> aging AWE32 sound card because it doesn't even have a digital input. Let 
> alone a half decent driver. Anyone got the jitters already?

Ghaaa!!!! I wander if all this jitter buissness is god for ya'!

> So If I'm going to salvage something from this mess, I've probably gotta 
> think of some ultimately cheap-assed way of distributing some digital-audio 
> signals. Any thoughts on this at this point would be greatly appreciated.

Well, splitting the signal can be done fairly cheaply. There is a
bunch of designs of variable complexity (and thus quality) around of
both input and output of signals. Apply them with extra many outputs
than inputs and you got yourself a splitter where you splitt up in the
digital domain in the box.

> Fortunately, I used GPS when I buried that hatchet.

So, you don't use a pirate's map anymore?

Cheers,
Magnus