Part 4 in the series on building a Lunetta synth with a Quad NAND CMOS chip. Now, we add a closed feedback loop through all NAND Logic nodes on the chip back to the first one. The result is an unpredictable, wild, and almost insane gate modulation.
Learning Electronics by Building DIY Musical Instruments
Part 3. In this post, we modulate the oscillator we previously built from a Quad NAND CMOS chip. We use another gate from this CD4093 chip to achieve this. All we need to add is another capacitor and resistor to modulate the second NAND operator by the first one.
We build the Bastl Skis Dual Decay VCA DIY kit. This neat little all-in-one decay envelope generator and VCA is a very handy tool for your Eurorack Modular. Plug in a sound source, trigger the skis channel, and dial in a decay time to get the volume shaped sound at the output.
Part 2. In this post we explore using the Quad NAND CMOS chip as an oscillator. This is actually a pretty simple circuit. We use the aforementioned CD4093 chip. All we need to add is a capacitor and a matching resistor to generate a square wave Lunetta style.
Part 1. Lunetta synths create sound by using digital logic chips. They’re very easy to build and so much fun. With just a few parts you can make a square wave oscillator, sequencer or noise machine. In this article, we take a look at the Quad NAND CMOS chip as a Lunetta.
I like gritty distortion. By using a couple of diodes to clip a signal we can build a passive clipper distortion unit. In this example, I use bipolar LEDs to do the clipping. Even though we end up with a drop in audio level it sounds pretty decent.
The final stage of the LFO Eurorack module is the output. This can be tricky. I examine how you can best design an output stage that plays nicely with other modules. Besides that, I also share some of the helpful insights I got from the synth DIY community on the matter.
With a constant current source, we can charge a capacitor in a linear fashion. We examine a simple constant current source circuit and how it works. We also touch the difference between linear charging and based on the RC-time constant.