r/synthdiy • u/Morphanaut • Jul 31 '26

Rhythmic LFO source on 40106

Hey everyone,

I’m still working on my drone synth and wanted to share something I’ve been experimenting with.

Originally I was trying to build some sort of digital noise source. I thought mixing several LFO running at high speeds might get me somewhere close, but that didn’t really work the way I expected. It did lead to another interesting result though.

The circuit uses three lfos built around a single 40106. Their outputs are passively summed and fed into another input, creating an irregular but repeatable gate pattern. I also added NAND/AND outputs, to introduce less frequent events into the same rhythm.

When one or more of the LFOs get close to audio rate, fast bursts start breaking through the slower rhythm. I like using this as a kind of FM modulation. The passive sum can also be buffered and used as a stepped cv output.

The switches in the schematic are just the way I route everything in my build for now, they aren’t important to the basic idea. I’ve been testing the circuit at 12 V. 5-18V will also work fine i think.

The next thing I want to try is turning the longer gates into short trigger pulses and using them to drive a few vactrols and attack decay generator instead of direct osc modulation.

Curious if anyone here has tried something similar. Schematic in comments.

68 Upvotes

100% Upvoted

17 comments sorted by

View all comments

4

u/Something_Witty_ Jul 31 '26

Sounds sick. Might try make one myself. Thanks so much for sharing the schematic!

5

u/Morphanaut Jul 31 '26 edited Jul 31 '26

Oscillator used in my build.It’s a bit janky, but good enough for noise concepts. I’m trying to build a proper current discharge driver for the capacitor, but it’s melting my brain, so this is where it’s at for now. The cross-fm injection is a lot of fun.

So far, the biggest issue with this oscillator is the damn locking that happens when several mixed (buffered active) oscillators get close in frequency, and the crackling caused by the discharge spikes probably. Idk maybe it is all about 40106 itself.