[sdiy] Using analog for physical modeling

[Matthew Smith]

Quoth Eric Brombaugh at 22/09/11 00:08...
...
> I've done a few boards for this sort of thing using
 > low-end Xilinx Spartan3A parts.

How low-end? Wondering how much I can squeeze out of the 3AN part I have 
here, which has 50,000 gates. Sadly, it's the smallest of the Spartan 
3AN parts, but the largest that Element14 carries in a solderable 
package - all the larger ones are wretched BGA. (Digikey/Mouser are out 
of the running for me due to their arm-and-a-leg shipping prices for 
sub-$200 orders.)

I can get a better-sized Spartan 3E and store the bitstream in a 
Platform Flash device, but it's extra cost/board real-estate. Object of 
the exercise here is to see how much I can cram into something really cheap.

 > ...but for longer delays you'd probably want an external SRAM.

Think I'll incorporate a load of SRAM (which is cheap) into my DVCA, to 
add flexibility.

> ...good-quality audio codecs...

Something I haven't had anything to do with, up to this point. What's 
the advantage of an audio codec - is it that you get two (I guess 
simultaneously sampled) channels in and out all in the same package?

I was about to do the schematics for the 3A-based board, and was going 
to use discreted ADCs/DACs, but could certainly be swayed towards a
more optimal solution.


-- 
Matthew Smith

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