[sdiy] Re: how it all started

[Ingo Debus]

Hi,

enjoyed all your stories so much, so I'll add mine.

The first electronic sound-producing device I built was a square-wave 
oscillator made from a 7400 and a 74121. This was in the early 
seventies, I was 13 or so. I got this circuit from a book (which I 
still have). I think this was also my first experience with integrated 
circuits (I had built some transistor circuits before). It had a 
keyboard, with trimpots to tune the pitches. One of my first keyboards 
was four-notes, from a HO model railroad, the thing with some momentary 
switches in it, to control shunts and signals.
The 74121 offered variable pulse width, a thing I re-discovered much 
later, when I built my Formant. The pulse width could be made longer 
than the period time of the oscillator, and since the 74121 is not 
retriggereable, the pitch dropped by some harmonic intervals when the 
pulse width became too long. Thiis was not intended but sounded 
interesting.

Later I made a PCB for it that looked like a miniature modular synth. 
What could be patched were just the capacitors for the oscillator and 
the monostable to set different pitch ranges.

Ingo