synthgeek's blog

Here is my latest little standalone noisemaker:

This is a small 3-oscillator logic synth, based somewhat on the same concept as the TrigPulser module in Loid. Like the original TrigPulser, it is based on the CD4093 quad 2-input NAND Schmitt trigger. In this synth, one oscillator is turning a second oscillator on and off, and the second oscillator feeds one side of  a NAND, while a third independent oscillator feeds the other side.

Here’s the schematic:

The range of sounds it can make is pretty amazing- though it can do the beepy & droney stuff you might expect, it can also do much more (especially when controls are swept)- harsh static-like noise, vocal-like sounds, oscillator-sync type stuff, etc. Here’s a couple of demos- audio, then video:

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As I once again need more money for parts, this one is going on eBay- I do plan to build one for myself as well though.

This came about while messing around with a CD4093 on the breadboard- I patched it up to an existing 3-input NAND gate already existing in Loid, along with a momentary switch for triggering- and cool stuff started happening.

The basic idea is based on the NAND gate in the 4093, which allows you to create an oscillator which can be gated, manually or via another logic signal. Having one gated oscillator is fun, but what happens if you use the old diode-gate trick on top of regular old gating. That was pretty cool too. Purely by chance, I hooked the two up to a 3-input NAND gate as shown in the schematic, and thus the Trigpulser was born.

Since the 4093 has 4 NAND Schmitt triggers, and a CD4023 has 3 gates, that meant the module could have two “sides”, and a final NAND gate on the output. I decided to build it so that the two sides could be used independently, or together through the final gate.

Here’s a recording of one side being used alone, triggered with two squarewaves from “normal” Schmitt trigger oscillators:

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…and here’s one of both oscs being used with the final NAND gate (the pauses are naturally occurring from the material used as trigger inputs):

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…and here’s a bonus video of a single side in use:

I will also be designing a stand-alone version of this, with a 40106 providing material for the trigger inputs.