diy GM synth

[Mikko Helin]

Hi there,

The Crystal chip is quite limited, IMHO. It even lacks the portamento
switch (though there is the mono mode). More interesting chip is
the Atmel/Dream SAM9773, which implements Roland's GS mode
with tweakable filter cutoff etc. (you can use pitch bend midi
messages for less zippery realtime control of Fc). It's also
got 20-bit I2S output. It needs the opto + 9.6 MHz crystal
or oscillator, which I haven't found yet. Could we design
our own pc-board for that chip, and order some chips
from Dream? Could this be the first digital synth-diy list
project synth? We would need a pcb manufacturer (was there an 
inexpensive place in Poland?), also some DAC's (see below). 
You can use two DAC's for 4-channel output in SAM9773, so you 
can route some MIDI channels to front DAC and some other
to rear DAC. To get most of the 20 bit DNR it would be
better to design a two-sided pcb, which is diffcult to
do at home. The chip itself is in TQFP80 package, and 
CS4334 in 8-pin 150 mil SOIC case (smaller than CS4331).
CS4340 is in 16 pin 150 mil SOIC case, it may be better
choice as we don't have to order 300 chips.
 
I'm going to ask the prices for the Dream chip, let's
hope it's not too much.

Links:
http://www.dream.fr/products.htm  - dl the sam9773.pdf
http://www.nuhorizons.com         - Crystal DAC's;
                                      CS4390 $3.65 (min order 108)
                                      CS4334 $1.50 (min order 300)
                                      CS4340 $1.95 (min order 47!)

http://www.crystal.com            - CS43xx data sheets


-Mikko


---------
Guys,

    These look like part numbers from an outfit called Crystal Semiconductor Corp
in Austen, TX.  Maybe somebody can find there web site and get some more info.  I
recall they had some interesting music oriented chips.

Gene Z.



Paul Perry wrote:

> At 06:10 AM 24/03/99 -0800, Elliot "If Loving Midi Is Wrong,
> I Don't Want to Be Right"wrote:
> >Which chips?  Name, number, website?
> >
> CS9236 CrystalClear wavetable synthesiser (surface mount) Insight Electronics
>
> CS4333 stereo serial d to a convertor (surface mount) Insight Electronics
>
> The article was in March 1999 Popular Electronics (USA).
>
> Complete kit of parts and PCB $125 US from
> David Dudley, PO box 658, San Marcos, CA 92079-0658 Plus $8 shipping and
> handling.
>
> 'short' kit with only the 'weird' parts and PCB $70.
>
> That is all I know... havnt seen it, heard it, or built it.
> Looking at the board, the surface mount chips (and a few caps) look pretty
> easy..
> they arent like 100000 legs, its serial and only a few legs are used.
>
> Curiously, it is a single sided board, with the surface mount chips on the
> copper
> side of the board. This is a cool idea!!
>
> paul perry (frostwave P/l) Melbourne Australia