Interesting video by IMSAI Guy explaining the CEM 3340 VCO:
7 Likes
After watching this video and actually understanding a little of what the CEM3340 can do I had a little idea that I could possibly use the CEM3340 as a wave shaper for my AD9833 VCO and sure enough I got some good results. The AD9333 triangle is fed into pin 10 via a 470nf capacitor and it feeds the sawtooth converter.
6 Likes
I’ve left this alone for a while as the test was not so successful, the sawtooth crapped out and reverted to a triangle wave at anything above around 900hz, so I revisited this tonight as it was bugging me that maybe my input wave wasn’t perfect, biased etc.
No changes at first, I managed to get it to around 1khz, but after that triangles again. I was thinking maybe the timing cap needs to be in place etc, well placing a 1nf between the timing pin and ground did nothing, but then I sort of put the cap from pin 13 to ground and I noticed the waveform changed more towards the sawtooth I was after. So I biased the pin 13 with a 1.5m resistor to +12v and the waveform improved and I was able to tune the sawtooth to a clean waveform using the input level and bias offset.
I will experiment some more but now I can go in excess of 4khz and keep a clean Sawtooth that sounds good.
4 Likes
Would an AS3340 or V3340 work any better in this application?
I would argue it would only have to work well up to a fundamental of 10kHz, after that any harmonics would be beyond human hearing.
This is currently an AS330, I really don’t see why anyone would want to go above 5Khz to be honest, that was high pitched enough.
1 Like
Built another prototype board today
4 Likes