[sdiy] S/PDIF cable

[Batz Goodfortune]

Y-ellow Y'all.
         That's what I love about this list. As a simple question and 
suddenly find out there's more devil in the detail than you thought 
physically possible. Actually fascinating because I rarely work about 20K 
and when I do it's all ass. I use to look at the wave forms on the scope at 
work (when I did work) and wonder why the hell they never looked remotely 
like the text books. I use to wonder how 'n' hell the logic at the other 
end ever made sense of it. But wondering was about all I had time for in 
those days.

And I'm sure if I asked a question about DNA sequencing there'd probably be 
someone on the list who's involved in researching it. Or at least done it 
once or twice. If we were all in the same place at the same time, what a 
team we'd make. I'm sure the world would band together and start building 
pyramids to honor their gods in death.

Oh yeah. And for the record. My keyboard isn't water cooled but I do have 
to aircondition it. It is after all a microsoft keyboard and I've had to 
glue it back together as many times as one of their operating systems. And 
in case you're wondering, I'm wearing a wrist brace at the moment as I seem 
to have a little problem with carpel tunnel. But this isn't so much from 
typing it would seem but from a propensity to rest my head on my hand while 
reading hour upon hour of text each day. I really need to make some kind of 
prop for my head I guess. But anyway....

As I stated, I don't have a whole lot of choice in cable. So I can't 
acquire the exact right stuff. Plus I'm dealing with a few un-knowns. As I 
said, when I deal with anything about 20K it's pure ass.

What we have here is podule that allows 4 ins and 4 outs with balanced 
transformer couplings. But at the other end we have a bunch of stuff. One, 
the DAT machine is indeed AES/EBU. And it's even on a short leash. But the 
sound cards in the rack are another story.

We have a bunch of hoontech cards. 3 in all. These have reasonably well 
designed S/PDIF I/O. However despite having something of an I/O transformer 
on them, the RCA socket is still grounded. Not a whole lot I can do about 
that. And then there's the ol' AWE 32. I have no idea how they go about 
this but it's simply a couple of pins fed out from the EMU8000 chips 
somewhere. It wouldn't surprise me if this was just TTL level or something 
knowing Creati-Flabs. To do it properly I'd probably want to put a 
transformer on the end of that before flinging it out to the O1V but of 
course I'm not going to do that.

I've actually had this output working on about 3 metres of ordinary 
shielded before but I have experienced some problems from time to time. I 
think more related to the indirect connection to the Creamware TripleDAT 
card. And that's the other source. The now aging tripleDAT which is now too 
proprietary to be of  too much future value but yet represents a legacy 
from previous and current works in progress. The idea here is to feed the 
T-DAT into one of the inputs of the hoontech card and then they'll be 
synched together and hopefully co-operate. But they probably wont.

The only real transformer balancing act is at the O1V end. And this is what 
I have to work with. 3 square pegs and 4 round holes. I could make the 
cables shorter but for another problem, which is that I designed everything 
in here so it could be moved about. Ideally I would have a space behind 
everything allowing me to walk behind and re-patch and modify as necessary 
but I don't have that luxury. I put the mixer on this really cute old 
medical trolly thing which I bought from Robbie's of course, It really 
looks wicked. And the idea here is that it can be drug out into the sweet 
spot for some serious mixage.

At the moment though the O1V is simply forming the audio part of what is 
possibly the world's most complex television set. To watch TV, something I 
rarely do anyway, I have to boot up the big machine, call up the video 
capture system, turn on the video recorder, fire up the video monitor, 
bring up the audio system, punch up the line from the computer and finally 
I can hear and see television. But Hey, Any idiot can just buy a TV and sit 
in front of it. I had to go make it an art form.

BTW. Anyone know of a real cheap Time Base Corrector out there? :(

Anyway, the point is that the cables have to be extra long so that I can 
move the mixer about where ever I need it. Yet at the same time, trying to 
keep the growing cable loom neat. Not to mention when I need to move one of 
the racks to get behind them. So it looks like I'm pretty much stuck with 
75Ohm cable and a little voodoo.

Thanks for that. I really appreciate it. Fingers crossed. :)

Be absolutely Icebox.

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