[sdiy] TTL top octave generator, was: transistor substitutions for BC108, BC187

[Mike]

> > Has anyone got a very early copy of Elektor with a TTL composite top
> > octave generator in it?

> I have the german issue, would that help you? You're right, it was
> November and December 1974.
>
> You really built that monster? I built the "small" version with the
> TOS IC back then.
>
Yes - and I think I did it either with veroboard or perhaps wire wrap. I
needed to run my top octave generator 16 times faster than normal, and the
TOS chips I tried simply stalled on too fast a clock. My final version used
a PLL, (using a  Plessey frequency synth chipset I think) to lock the clock
to a crystal source when the pich bend was in the middle, but allow it to
come out of lock for pitch bendiing. The idea was originally for scan tuning
in communications receivers. I also used the Elektor idea of a gated
bistable in the master clock driven from an LFO to give an octave tremolo.
The source of it all was a fire sale I went to where the insurance people
couldn't get rid of a lot of  foam sodden TTL chips. I got 3 BUCKET fulls
for £3, (though that was a weeks spending monet then!). I took them back to
the hall of residence and washed them off  in the bath. Most of the
labelling stayed on, and my polysynth thing project began there. It finally
had a 20Amp linear power supply, lugged home on the bus from the famous Bert
Ault's shop in Birkenhead. The case and keyboard were from a burnt out Vox
'continental', I got from Frank Hessy's, paid for by repairing amplifiers. I
let a friend have custody of it when depression made an end of my student
career, and lost touch with him in the 80's. It had a 'normal' square wave
organ sound, a resurrected Vox drawbar system, and a 12 voice 'thing' that
'drew' waveforms with 16 slider pots, and I idea I saw, (I think), in a
keyboard played by Rob Jan Stips of 'Supersister'. Mine had 12 voice modules
and multiplexed the slider outputs. The envelope gens were crude, but
worked. I had a 'chord hold' for doing drones, and a sort of basic
arpeggiator. All done in LSTTL. My notes were in the binders I left with it,
so now I'll never know the details, it being so long ago, It was the first
time I ever had to put a fan on anything! It had a voice prioity system, up
to twelve sounds, or less if the hold was on, if you pressed more keys
nothing happened.  I spent more time modifying it than playing it, though
the guy who had it was a classically trained organist and liked some of the
tones it could make.

Around the same era, I did a drum machine based on a PE design, using 7489
RAM chips, (16x4 bits!). To do patterns I added another set of RAMs with
instructions in them. I found some of the sketches a few years ago, and
realised I'd kind of re-invented the stored program computer, with a kind of
Harvard architecture. I was a bit bipolar then, and would solve quite
complex stuff whilst on the upward curve, (usually to crash when I mentally
ran ou of gas), Still I got some interesting things done, just didn't know
how to publish them....

If you could email me a scan of the diagrams that would be very kind of
you - I want to remember why I thought it sounded interesting. Perhaps due
to some temporal jitter creating a mildly variant sound, I'm not sure.

Thanks. Hope I haven't bored too many peoplel with this trip through my
personal dusty archive.

Mike