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.

What is SaaS?

I recently got in a discussion on the Slack associated with the Hacking SaaS substack. (Which if you’re in the industry, you should definitely read!) The question was about what kinds of tools you should feel comfortable using if you’re an engineer at a SaaS business. The conversation then turned to the nature of: what …

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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.”

Wifi spectrum analyzer

An embedded device with LCD displays the wifi spectrum analyzer app

My latest gadget is a Wifi spectrum analyzer. Built on the Wio Terminal by Seeed Studios, it was a simple embedded device to set up.

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.