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RE: So you DID have...

Posted by Jim F. (A) on December 22, 2009 at 21:53:45

In Reply to: So you DID have... posted by Presto on December 22, 2009 at 17:25:55:

> - 24/44.1 Toslink S/PDIF out from Prodigy 7.1, ASIO driver

This should have been written
"24/48 Toslink S/PDIF out from Prodigy 7.1, ASIO driver".
(At this point, I've already run Saracon on the 32/44.1 file from
Wavelab.)

> why go from 16 to 24 bits with software, then spit out 24 bits
> from the Prodigy. . .

I go down to 24 bits fixed-point from the 32-bit floating-point output of Saracon
because that's the widest output any sound card can take.

> . . .only to go back down to 16 with Meridian 518 #1

Because of the limitations of Audio Alchemy EDR*S. It's strictly
16 bits in and 16 bits out (I had to learn this the hard way --
nobody told me this beforehand.) I **really** like the sound
of EDR*S, and don't want to do without it in the chain.

See the Usenet post from 1996 by somebody who heard the EDR*S
system at the Stereophile show in New York in 1996:

http://groups.google.com/group/rec.audio.high-end/browse_thread/thread/44659620494e458e/90d03717d9b252bd

(Gabe Wiener and Steve Zipser are no longer with us.)

There was also a guy named Thomas W. Shea -- quite a serious record collector,
apparently -- who had an EDR*S system built for him by Audio Alchemy. I tried
to contact him about it, but he's disappeared. There were some letters
from him about all this posted in Stereophile, back at the time.
He also posted an inquiry on Usenet:

http://groups.google.com/group/rec.audio.pro/msg/02681dcf8123b7bf

(He never realized, poor guy, that he didn't **need** a 20 bit recording
capability to capture the EDR*S output, since it only outputs 16 bits. Of course,
he didn't have access to software DAWs with their bit meters, either.)

Meridian #1 dithers the 24 bits from the sound card back down to 16 bits,
noise-shaping over the bandwidth provided by the 48 kHz sample rate,
and then feeds those 16 bits to the first EDR*S box.

> And... why did the Big Ben go where you put it in the chain?

The Big Ben is where it is because the output of EDR*S is **extremely**
dirty. Peter Madnick warned me about this -- he said I'd probably
have to play musical chairs with the consituent 8 DTI Pro-32 boxes
until I happened to stumble on a sequencing that would produce
a usable output from the last DTI's S/PDIF output (the boxes themselves
are all hooked together with I2S; the first one also gets S/PDIF).

Even an RME ADI-192DD couldn't sync to EDR*S. Fortunately, the
Big Ben has no trouble syncing, and even achieves narrow lock.
Phew! And it worked the first time -- I didn't have to waste hours
or days playing Permutation City with the 8 DTIs.

> Or are you using the big ben as a masterclock for downstream as well?

The only master clock (in the workstation chain -- we're not talking
about the EMU-1212 slaved to the Rosetta 200, here) is the
clock in the Prodigy sound card itself. Everything else is clocked
from its input, whether S/PDIF Toslink, S/PDIF coax, AES-EBU balanced,
or I2S (and they're **all** there ;-> ).

Even with the Big Ben, though, the EDR*S boxes are **very**
touchy. Once they're up and running, they're stable for days.
But if the power goes off, it's a **major** Pain In The A**
to get them all going again -- some of them will not boot up
if they're connected to their neighbors. So its a matter
of starting them up one at a time, and then connecting them
up to their neighbors via the short I2S cables after each one's
DSP has booted successfully. If the boot is not successful,
all the LEDs on the box come on and the processor
just locks up. I had to discover all this more or less by
trial and error. This is **not** a commercial product!

I'm still amazed that Peter Madnick and Mark Schifter were
willing to do this for me -- I paid for Madnick's time and
use of the intellectual property, of course. He had to go
digging up the DSP code and then burn PROMs. I installed
the chips in the 8 DTIs myself, removing and saving the stock
ROM chips. One "little" glitch along the way -- in the
original PROM shipment Madnick sent me, **every other**
chip failed to work. There was some sort of systematic
problem with the partitioning of the code, apparently.
But he figured it out and sent me 4 "odd" ROMs (or "even"
ROMs, I can't remember which) that worked.

Yes, it was worth the trouble. ;->

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