MOTM

You can try this, but it's much easier to buy a 12 to 16 bit D/A
converter.  Basically the problem you're trying to solve, D/A converter
accuracy, has already been perfected by IC designers over the last 20
years.
John Loffink
jloffink@... 
-----Original Message-----
From: J. Larry Hendry [mailto:jlarryh@...] 
Sent: Tuesday, February 19, 2002 10:45 PM
To: MOTM List
Subject: Re: [motm] Quantizing
 
I have l long been thinking about a quantizer.  My thought process was
that a very accurate circuit could be built in the 8 bit format IF one
used a ADC to get the digital quantities, but avoided the 8 bit DAC by
going completely analog on the output.  Then each of the 8 elements
could be trimmed accuracy so when you added the elements each together
you would have much greater than the accuracy expected from a 8 bit DAC.
I can see Paul shaking his head and sighing at me right now.  But, I
have been thinking seriously about a replacement for the 822 when those
PCBs are gone that uses pots instead of rotary switches.  So, trimmer
count would be considerable less.  Of course, then your basic circuit is
a quantizer.  I have done no development yet because of other projects,
my need to learn more, and the (cough, cough) significant stock of 822
PCBs I would like to make a dent in first. :)  And, I fully admit to
knowing almost nothing about it and being significantly under-qualified
for the job.  So, I'll probably play with it anyway.
 
On a related question, where would one normally expect the analog out to
track the input relative to step points.  To simplify the example, let's
assume 1 volt steps.  Would the output be desired to change from 1 to 2
volts at 1.5 or 1.9999 on the input?  I don't see that is really
matters.  But, I am still pretty ignorant on the subject.
 
Seems the 8 bit DAC might be fine for a mono synth and single
oscillator, but would never do where oscillators might beat together.  I
have a couple of the PAiA 8 bit MIDI 2 CV 8s that I use with stuff other
than my MOTM modular.  For my mono synths (like my Micromoog) that 8 bit
resolution seems to be OK.
 
Larry