Super Simple Quad Saw/Pulse VCO out of one 40106

[synthmonger]

I haven't tested more than three VCO's running at a time from a single 40106 but it works pretty darn well! There is some very minimal bleed-thru but only really noticeable if you're trying to hear it. Tracking can be a bit iffy!

I haven't tested the sync with oscillators other than 40106 VCOs but it seems to work pretty well. I may come up with a slightly more sophisticated sync method using Fet switching or something. If anyone encounters problems please let me know!


You can leave off the Pulse width op-amps if you want just a Saw VCO. You can also use a quad op-amp instead of duals. They must be TL072 or equivalents. LM358 and the like aren't suitable replacements.

I did plan on making it 3 VCO's using two hex inverters. One for the saw core the other for the pulsewidth modulation but I could only get 1-50% duty cycle or 50-90% not 1-100%.

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[widdly]

Thanks for posting.

I built one of your earlier 40106 designs and I had a problem with it. It stopped oscillating at the top end of the CV scale, but before it went out of my hearing range. Have you noticed this? I was looking to use one for a simple VC clock.

[synthmonger]

Yeah it happened to me because of bad a transistor and I think it also happened because one was reversed.

[synthmonger]

I did some more tests with this module and found that a max of 4 stableish vcos are obtainable. Any time you're using the inverters next to each other will cause some annoying bleedthru and unnecessary cross modulation.

Anywhos if you the following pins you will be set.
1-2
5-6
13-12
9-8

Ground pins 3 and 11

[richardc64]

Since you say to ground pin 3, I believe you meant to say use pins 5-6, not 4-6. No?

[synthmonger]

Yes my mistake. I edited the post to reflect the correct pins.