[lug] Rehash: Ethernet Sound Card

[Nate Duehr]

The December issue of Elektor Electronics magazine from the UK has an
article on how to build a USB to S/PDIF optical input/output audio board,
powered from the USB bus... (it also has analog-input/output).

It's not exactly what you're looking for, but it has a good discussion of
various issues surrounding building this type of thing.  Kinda.  It also
would be a good start on a working circuit to try other things, like adding
Ethernet.

The only place I know to get this magazine locally is at the store called
"The Newsstand".  Unfortunately you'll pay for the privelege... $12.95 US if
you buy them there.  The joys of a relatively rare imported magazine.

(However, if you're into this sort of thing, I find the quality of Elektor
to usually be much better than the three or four American electronics
hobbiest magazines combined.  Lots of real circuits, and the articles are
missing the "my life story and why I decided to build this thing" text that
usually takes up at least a page of the U.S. magazine's project articles.)

There are now a number of Ethernet chips that have a raw UDP capability if
passed a data stream at the appropriate bitrate.  They are less than $10 in
low quantiy.  Mixing one of those with one of these designs, one could
possibly get what you are looking for.

Of course, to meet the Ethernet specs, you'll need buffering.  Collisions,
etc... and you'd lose audio.

Still seems like quite a chore to design this correctly, but the hardware is
out there now to do it.  Perhaps you can find a willing EE who wants to give
it a whirl.

The DAC chip used in the article is the PCM2702 from Texas Instruments.
Datasheets are available at www.ti.com and the chip does enforce the Serial
Copy Management System (SCMS) which will force a switch to the analog input
if the chip detects the copy-protection bit pattern passing through the
optical inputs.

Well anyway, there's ton's more info in the article.  It'd be a good place
to start tinkering, I suppose.

To move it over to ethernet you'd need one of those Ethernet chips, and a
microcontroller  capable of handling "traffic cop" duties and initialization
of the Ethernet device including storing an IP address, etc... and various
other stuff... not the least of which would be a lot of bench time to tinker
with it... but stuff's out "there" that could do your application now; it
appears that way, anyway.

Nate, nate at natetech.com

> -----Original Message-----
> From: lug-admin at lug.boulder.co.us [mailto:lug-admin at lug.boulder.co.us]On
> Behalf Of Peter Hutnick
> Sent: Wednesday, January 08, 2003 11:05 AM
> To: lug at lug.boulder.co.us
> Subject: Re: [lug] Rehash: Ethernet Sound Card
>
>
> > I saw the /. post this morning too. It looks similar to the slimp3
> > player (http://www.slimp3.com/). Check it out if you haven't, it might
> > interest you.
>
> Nope, this still has the same old problem.  It is a /decoder/.  I'm
> looking for a device (like the one on /.) that just takes plain old PCM
> (over plain old Ethernet) for input.  This thing plays MP3s.
>
> My dream device is not aware of MP3 or OGG or anything.  It would,
> therefore, play files encoded in codecs that don't even exist yet without
> a firmware upgrade.
>
> Beyond that the slimp3 has an IP stack!  What's that for?
>
> -Peter
>
>
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