[LAU] open hw soundcard with ext. codec

[Karl Hammar]

Martin Homuth-Rosemann:
...
> Hi Karl, hi LAU users

Hello and welcome to the discussion.

> I've followed the discussion about timing and synchronisation - what do you 
> think about separation of number crunching and communication (ATNGW100) from 
> the "dirty business" of ADC. 

Shall take that as a question (you have no ?)?

Don't you always have to separate the digital and the analog domains?

My plan is to build a card frame based system with one main power
module, one cpu card, with the possibility to add a lot of different
i/o cards. One such card could be for audio input/output. (Although
my main interest is industrial measurement and control.)

With this the "dirty business" of ADC is separated to another card
like an ordinary old soundcard you attached to your motherboard.

Do we need more separation? Could it possible be because of:
. space constraints
. noise and audio quality
. power constraints
. economical factors
. "time-to-market"
etc.

What are the key factors for you ?

> We need the codec, some kind of amplification, a clean power supply etc. to get 
> a good S/N ratio - and we need it for a lot of channels. 

Do you have a spec. which you'd like to discuss ?
E.g. how many channels are you regulary using, what s/n ratio is a
minimal requirement for you ?

> There exist many (more or less) pro-audio devices with well documented 
> interfaces (SPDIF/AES-3; ADAT; MADI)

Is your point, that the system should behave as an spdif etc.
device instead of delivering the audio over ethernet?

SPDIF [1], seems to be able to carry 20bit (maybe 24) 2 or 4 channels
at 44.1 or 48kHz (possible other) sampling rates.

AES-3 [2], seems to have the similar (24bit though) carrying capacity.

ADAT [3], seems to be limited to 8 channels at 48 kHz, 24 bit.

MADI [4], seems to be limited to 64 channels at 96kHz, 24 bit.

If this project shall implement any of theese interfaces it might
then be the ADAT or MADI, since I see no reason to implement the
smaller interfaces.

But if we successfully implement adat or madi, we are still missing
the adat/madi part on the pc. So we still have a problem...

And if we get i/o capacity problems with ethernet, we could easily add
another ethernet card at relatively low cost. But then you might find
that the rest of the computer is to small.

> - a cheap one is e.g. the Behringer 
> ADA8000 for about 200 ¤ [1] with eight mic (phantom power) or line inputs and 
> eight line outputs. The codecs are 24bit at 44.1/48 kHz [2] 
> 
> [1] http://www.thomann.de/gb/behringer_ultragain_pro8_digital_ada8000.htm
> [2] http://images4.thomann.de/pics/prod/164573_manual_eng.pdf

Are you suggesting that that unit's spec is something to aim at ?

Or is your point that it would be better to do a ADAT, or MADI
interface for the pc instead of doing a "soundcard" ?

Doing a adat/madi interface for the pc is  outside of the scope of
my projet, so I cannot help you there.

Regards,
/Karl

[1] http://en.wikipedia.org/wiki/S/PDIF
[2] http://en.wikipedia.org/wiki/AES/EBU
[3] http://en.wikipedia.org/wiki/ADAT
[4] http://en.wikipedia.org/wiki/MADI

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Karl Hammar                    Aspö Data               karl at aspodata.se
Lilla Aspö 148                                                 Networks
S-742 94 Östhammar          +46  173 140 57                   Computers
Sweden                     +46  70 511 97 84                 Consulting
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