Moog 921B sinewave

[jorgen.bergfors at idg.se]

Hi all.
I got my copy of the Moog 921B triangle to sinewave converter working in the 
weekend.
I run it on +-15V instead of +12 and -6 volts. That meant changing most of the 
resistors.
The circuit is quite different from the commonly used diode-based waveshaper. 
This circuit uses four transistors from a CA 3046. Moog used a more 
conventional circuit with four diodes and resistors in the older 901 VCO. They 
must have felt that this circuit produced better results.
Indeed it does produce a sine wave that can be made to look quite good on the 
oscilloscope. I haven't compared directly with other sineshapers though. There 
is two trimmers to adjust the waveform. One adjusts the "drive". It makes the 
wave rounder if you turn it up all the way. It doesn't get flatted at the peaks 
though. The other trimmer adjusts the symmetry. There is also a trimmer for 
adjusting the DC offset at the output.

/Jorgen 

P.S. Those of you who requested schematics for my version of the saw to 
triangle converter will get it and the sine converter circuit shortly. I just 
want to test it with resistors from the E12 series first. Currently it uses E96 
metal film resistors, because that's what I had available. I will continue to 
use 1% metal film resistors, but I think it would be better to standardize on 
E12 values.