[sdiy] Buchla 266 fluctuating voltages

[Peter Grenader]

My good synth chum Cynthia was kind enough to donate a 5837 she had to a
worthy cause (me), and I went ahead and built an 'inspired by page three of
the 266' module (uh-hum).  It works like a charm, but...

Any of you thinking of making one might want to jot this down:

You'll be much more pleased with the results if you replace the documented
100K pulldown at the output (after the diode) with a 220k to -15 instead.
It will increase your voltage range by about 4+ volts, which tends to vary
randomly only between 5 to about 7 without this.   And this range gets even
crummier (narrower) when you speed it up. This resistor mod will give you
true random between about .5 to 7+ regardless of the speed and it rocks.

I opted to not only bring the -3db, flat and -3 dB digital noise out to the
faceplate, but the noisey triangle wave as well, which is the heart of the
fluctuating voltages and really really fun as a source of stepped random via
a sample and hold.

I have one small snaafu yet to fix - tit seems the vactrol controlling the
556 r/c is such that the thing will crap out (stop oscillating) if you bring
the pot lower than about 2K in its range.   Simple matter of pulling out my
dog eared 555 cookbook to see what I've exceeded and I'll get to this during
the week sometime.

Cost of parts (sans the 5837) - 22 bucks and change at Mouser, including
pots, knobs and jacks.  Quite a bargain.  I'll see if I can post a soundclip
in a couple of days.

- Peter