CD series sub oscillator

KOSMO MODULES
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While not entirely in Kosmo format, I thought I’d share something I’ve been working on.

It’s a sub oscillator based on some old school CD4000 series CMOS logic - that’s where I read about the CD4026 that Sam used in his googol [ thanks @eric ] counter.

This thing will take in a signal and spit out an octave below, with an optional fifth or octave above.
Here’s a demo of a prototype:

Still a few issues to fix up, but you get the idea.

Here’s the schematic - have at it. First one to turn it into a functioning Kosmo module gets a cookie.

cd_sub_osc-1
cd_sub_osc-11755×1242 162 KB

Cheers,
Jared

5 Likes
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That’s a googol counter.

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I built one based off the simple version described here, which is apparently originally based off the Sh-101, for my K25 subosc:

It uses a CD4013. Very barebones compared to your design; no multiplying, no square conversion on input(it really only takes sawtooth or square wave input) no onboard mixing etc, but it sounds great!

How accurate do you feel the frequency multiplier is? The PLL part of the circuit. I was thinking about making a clock multiplier, but would have to be damn near perfect on the timing

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The SH-101 idea of creating a couple of octaves and diode OR-ing them together is neat! Might be interesting to try something similar with the waves already there.

At the moment I’ve only been feeding it the square wave out of my VCO - I don’t really know how good the square conversion is.

Haven’t measured the frequencies exactly, only eye-balled and listened to it. As I’m using it for audio I don’t mind if it’s a little off and it sounds a little detuned. When I last checked on the scope it looked pretty good, and it can snap there pretty quickly - might be worth trying for clocks. You’ll have to bump up C1 I think to track the lower frequency ranges better. You’ll only get one multiplication though - so I reckon you’d multiply up x16 and then divide down a few times to get the others. If you try it out be sure to report back and let us know!

Cheers,
Jared

1 Like
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Thanks for the advice! Basically I’m torn between figuring out an analog solution (PLL) vs arduino/software implementation, but I don’t know much about coding

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These days every website says that (often times I can’t even enter the website without accepting it), so you better offer something more special !

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