[sdiy] DACs for Arp-style quantizer

[scottnoanh at peoplepc.com]

Interesting, indeed, I'll have to give that a shot.  I ended up dropping the
latches on the one I have on breadboard - I found that cascading two
synchronous CD4516's worked just as well.  I compared the performance of
that with the CD4024 which was latched on the rising edge of the clock
(after advancing a count on the falling edge of the clock).  My comparison
was simply running an LFO through the quantizer and listening for
glitches/missed steps.  The two versions worked identically, so I stuck with
the cascaded 4516's because it was one IC less than using a 4024 and two
latches (using 7 bits, I had a choice of two 4 bit D latches or two six bit
D latches).

Fat bit of good that did me - my comparator/LF398 triggering scheme works
very, very well, but is extremely top-heavy parts-wise.  Believe it or not,
I found that swinging an LF393 in -15 to 0V range, inverted by a (brace
yourself) TL072 inverter into a section of CD40106 for pulse width
conditioning worked amazingly glitch-free.  Bad thing is I couldn't use both
sections of the 393 for two different channels - there was enough
bleed-through to cause glitching between channels.  My clock is running at
35 kHz, BTW.

Gory details are here (they're in a PDF):

http://mypeoplepc.com/members/scottnoanh/birthofasynth/id15.html

I'd love the EPROM approach, but I have not a burner, nor the chops to
program it.  For this app, I needed four channels (that's a whole other ball
of wax).

Chars,
Scott