analog to digital

[Stopp,Gene]

There's a real simple 4-bit flash converter that was designed by John
Simonton of PAiA and published in Polyphony a while back (at least I
think it was John's design, maybe Marvin's or Thomas' or ?). I think
that it was even offered as a little PCB from PAiA.... check the web
page.....

Anyway 4 bits out of a quad op-amp, maybe it was a 3900, I ferget... it
used come clever feed-forward and feed-back resistor networks... ah yes
network... I even think it was referred to as a "Neural Network A/D
converter". Somebody help me if I'm a little off here.... Anyway for a
4-bit flash converter using the traditional approach, you would need 16
(15?) comparators in a row with a 16-to-4 encoder, so this was a nice
little trick.

And lo and behold, this very topic neatly ties in to our recent
discussion about Dual Pulse Waveform Shapers - turns out that Ian
Fritz's DPWA in Electronotes (yes I looked it up and guess who the
author was!), as modified by me to add two more comparators for a "Quad
Pulse Waveform Shaper", turns out to be just another flash converter
with voltage-variable converging and diverging switch points. And yet
another thread is touched, as we discover that the recent topic of a
bit-dropped A/D-D/A converter for quantizing triangle waveforms yields
the same odd harmonic spectra, although unchanging over time.

Neat huh. Maybe we could come up with a Neural Network Bit Dropped
A/D-D/A Odd Harmonic Multiple Pulse Voltage-Controlled Switch Point
Waveform Shaper? So along with DPWS and MPWA and PURTWEE we can have a
NNBDADDAOHMPVCSPWS?

The coffee is just kicking in.

 - Gene

 ----------
From: mark verbos
To: Synth-DIY
Subject: analog to digital
Date: Friday, May 22, 1998 4:49AM

Does anybody have a schematic for a very simple 4 bit analog to
digital converter. I wanna add Buchla style voltage controled
stage select to my sequencer. All the AtoDs I have found were
elaborate circuits, way too much for my needs.
 --
mark verbos

"I think the future of analog modulars is to build them
yourself."