electronics

The GS-101 analog synthesizer project

A set of Eurorack synthesizer modules on a desk top

Ironically, since I’ve spent so much time working on this project, I have not posted about it much—but I’ve spent a huge amount of my free time in the past two years or so building a complete analog synthesizer. From scratch. And now it’s really starting to come together!

Gremblnote Application Note GN-0001: OTA-based Automatic Gain Control (AGC) Circuit

Schematic diagram for Automatic Gain Control (AGC) circuit)

I developed this automatic gain control (AGC) circuit to compensate for the -3 dB gain after each filter stage in a 2-stage, 4-pole voltage-controlled filter (VCF). I’m posting this because it was surprisingly difficult (rather, impossible) to find a low-distortion operational transconductance amplifier (OTA) driven AGC schematic I could use directly.

Precision current reference

A precision current source like you’d find in an SMU would be a very helpful tool for some of my other projects. But an SMU costs an arm and a leg… my needs were not so great. Could I make what I needed without breaking the bank?

Audio hardware Development Breakout Board

Over the past year I’ve gotten into building modular synth components. There’s a lot more to share on that front; I’ve put together several modules and have a plan for several more to go into an integrated system. The relative complexity means there’s a lot to write about, though, which has made me keep putting it off…

In the meantime, I completed a smaller project this weekend—a breakout board that makes it easier to develop audio circuitry on a breadboard.

Luminous Gates

An electronic circuit on top of a wooden box, with illuminated wiring

In a recent blog post I described building a more powerful EL-wire driver based on the 555 timer. That was in service of a small art project which I finished last week, “Luminous Gates.”

3-D printed case for Raspberry Pi & LCD

A 3-D model of a case for a Raspberry Pi and LCD screen (not shown)

I recently designed a custom case to fit a Raspberry Pi 4 and a 7″ LCD screen. I wanted a small tablet-like computer I could set up to look at while seated at a table, or standing at a counter in the kitchen.