[sdiy] CEM3340 question -- interpolating scanners (again)

David G Dixon dixon at mail.ubc.ca
Fri Dec 4 06:33:40 CET 2020

Hi Bernie,
The scanners work very well at audio rates.  The one I posted the pictures
of is all TL07X opamps and 2164 VCAs -- all things that operate very well up
the audio range.  I don't actually have that scanner anymore -- I built it
for someone else and he took possession of it, but maybe I'll dust off one
of my other scanner designs and try it.  I think I still have an 8-channel
scanner somewhere.
Incidentally, my 4- or 8-channel scanner based on crossfading and channel
switching is easily expanded to more channels.  Indeed, I built a 32-channel
scanner from a 4-channel scanner and four 8-channel scanners all controlled
by the same controller -- a 4x8 matrix scanner.  This I installed in one of
my "Polaris" multimode filters to get 32 different filter modes.  It worked
well, but the module was literally a foot thick, because there were more
than a dozen PCBs all bolted together.  I actually gave that module to a
local musician buddy of mine (he was thrilled, and I was happy to get it
outta my garage).


From: Bernard Arthur Hutchins, Jr [mailto:bah13 at cornell.edu] 
Sent: Thursday, December 03, 2020 7:28 PM
To: synth-diy at synth-diy.org
Subject: [sdiy] CEM3340 question -- interpolating scanners (again)

[CAUTION: Non-UBC Email] 

David -

In your video of your scanner you seem to be scanning at a sub-audio rate
exclusively (?).  Thus your output is a sequence of notes (short tunes) with
each pitched note having several-to-many cycles.

Have you tried scanning at an audio rate?  Specifically, what if each
channel was a different waveform from the same VCO and   the scan rate were
at an audio rate (perhaps 8 times higher than the VCO PLUS, say, 1 Hz)?
Each VCO waveform would be visited slightly faster than once per cycle in an
evolving manner.  Wouldn't this produce an "animated" output perhaps similar
to my "Tone Wheel Animator"?  


Thanks   -Bernie

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