Synth-diy-test

TL071 op-amp dropped straight into the SH-09 and it works a treat.  One 
minute after releasing a note the pitch now only drops by about 15 cents. 
Not bad for an analogue sample & hold.

I also fixed the issue with the improvised sub-oscillator divider triggering 
on the wrong edge of the VCO waveform, (the PWM'ed edge,) which was 
imparting an annoying pitch warble on the sub-oscillator.  I made a little 
PCB with a 4013 dual D-type flip-flop chip on it to replace the original 
(missing and unobtainable) DN819 frequency dividers.  It sounds much better 
now.

Don Tillman you were right with your prediction of which edge that old I2L 
divider chip was clocked on! :-)  Many thanks.

-Richie,


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