On 4/4/06, Jack Carroll <[EMAIL PROTECTED]> wrote: > On Tue, Apr 04, 2006 at 09:14:44AM +0100, Paul Mullen wrote: > > > > One concern is that you will need to build a breakout box for your A/D > > converters or else rely on someone else's converter box and just support > > something like ADAT lightpipe I/O but at that stage you have pushed yourself > > downmarket unless you add something to differentiate yourself like a DSP > > farm. > > Well, speaking as an old analog instrumentation engineer, my instinct > would be to push the A/Ds right up to the mike connector when you're trying > to achieve that level of precision. The cable alone is a major error source > when you're playing in that league. You get half a dozen kinds of > electromagnetic coupling right through the shield, triboelectric noise, and > on and on. So it's not a card design problem, it's a total system problem. > And I sure wouldn't try to design the DACs and A/Ds for that performance > level; there are engineers a lot smarter than I am who've spent a whole > career doing that. And it doesn't cost all that much to buy the resulting > chips off the shelf. > I'd say the place to start with something like this is in the market > research. Begin by finding out what the users need and want, and what's > already out there. It might be best to design around remote analog hardware > that already exists, and pick up the signal already digitized to build an > open-ABI hardware platform.
Here's a whacky idea: Ever seen a Matrox dual-head card? It's got an LFH60 connector on it. We put a pair of those on the the card. Lots of pins. And we make all of the signals DIGITAL. Just like with DVI, we use LVDS signals to transmit the channel data out to the connector. Connected to each LFH60 is an adaptor for a four-pin connector (power, ground, signal+, signal-). Then, right at the audio device, we have another adaptor that has its own power isolation and converts the audio from digital to analog right there. The signal's only analog for about an inch plus whatever is inside of the other device. Mind you, we'd need to have lots of cheap LVDS to analog 32-bit DACs. Another idea is to do all of the synthesis and signal processing stuff on the card in the FPGA, but all the signals come out digital, connecting to an external box that is thus isolated from the noise. But being one unit, it's less expensive than the totally separate solution. (With separate DACs, we lose the ability to use sigma-delta directly.) _______________________________________________ Open-graphics mailing list [email protected] http://lists.duskglow.com/mailman/listinfo/open-graphics List service provided by Duskglow Consulting, LLC (www.duskglow.com)
