apologies for the late reply on this!!! drowning in projects haha.
ok so I took a look this evening, the initial issue with the CEM chips is pitch drift when pulse width is adjusted it happens here and there and its a bit hard to predict in what situations it will happen, sometimes it does sometimes it doesn’t. in the 1222 it runs from 0%to about 33% duty cycle. from my understanding you want about 50 so then its the full amount.
issue with this was a slight pitch fluctuation. And in mk2 of the oscillator (currently sat with another 6 or so nearly finished prototypes, its a dual oscillator around 1 tuner) I went for an external comparator to make the square wave to make it not an issue
BUT!@!!! I just came across an idea that will sort it 
however I need a few guinnee pigs to see if this works for everyone!
ok so here goes. there is a reference image below. (this 1222 varies as its an old prototype hence it has bits hanging off it and chopped components etc)
FIRST swap R13 which is a 470k with a 200k, 220k is fine but 200k will get you closer to 50 percent duty cycle.
right that’s it, for the most part this is perfectly fine, in a set of 3 oscillators you won’t notice the minor minor pitch shift that happens when you adjust the pulse width
BUT I FOUND A PROPER PROPER DODGY BUT MAYBE QUITE A GOOD SOLUTION.
so it got me thinking maybe there is a way to counteract this externally to the CEM3340 reduce the pitch change well infact there is!!
put a 20M resistor (I didn’t have one so used 2 10M’s) between the two solder points circled in red.
what this does is it also sends the voltage going to the PWM pin on the 3340 to the pitch input too! just enough to counteract the pitch drop.
for some people thinking this may cause the pitch controls to bleed into the PWM yes it could do but it is so so small it isn’t noticeable, on my max zoom on my oscilloscope I did not see. but to be honest oscilloscopes are over rated on synths! like they say IF IT SOUNDS RIGHT IT IS RIGHT :D.
anyway! let me know if anyone dares trying this! I’m gunna continue testing it.
