[sdiy] Triangle wave octave generation (frequency doubling)

[Tom Wiltshire]

Hi all,

Once upon time, long, long ago, I built a little circuit which  
consisted of a triangle wave oscillator followed by a series of  
precision fullwave rectifiers (the op-amp based variety). The  
rectifiers folded the bottom half of the triangle wave up and thereby  
doubled the frequency. With a bit of trimming, I was able to get  
about 4 octaves above my input triangle wave out of this before the  
waveform quality began to suffer.

Looking at those SH2000 schematics this morning reminded me of this  
early experiment with frequency dividers/doublers.

Does anyone know any synth/organs that have used this triangle- 
folding trick? I've often wondered why more organs didn't use it,  
since they often filter the square waves from flip-flop dividers to  
try and get sine waves - you'd get a better result if you started out  
with less harmonics to begin with.

Thanks,
Tom