[sdiy] Buchla 266 Quantized Random Voltage

Pete Hartman pete.hartman at gmail.com
Sat Dec 14 07:17:53 CET 2013

I'm troubleshooting one of Roman's 266 clones, and while I understand
what the QRV is supposed to DO, I don't yet grasp entirely HOW it is
supposed to do it.

The behavior I see is that on the start of my clock, I get quantized
voltages, correctly varying among a number of steps based on the input
pot, for 20 clocks.  After that I get nothing, for as long as I've
been able to observe.

I understand that we're looking at a shift register.  I've read Dave
Brown's discussion of the startup voltage to start things off with all
1's....what I suspect is happening is that after those ones are
shifted out, I'm only getting zeros in.  But I'm not grasping (at
midnight anyway ;-) ) how I might test that hypothesis, nor how it is
that it should be getting things that aren't zeroes shifted back in.

I've googled a couple of things trying to find something discussing it
in step by step detail, but found nothing.  I scanned Bernie's
Electronotes article about random voltages from issue #64, but nothing
jumped out at me as matching the topology (though I do see he talks
about shift registers, so when I'm more awake I will try to read it
more closely).

But if anyone knows of a resource where this is discussed in more
detail, I would very much like to read it.



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