DIY SYNTH VCF Part 3: Resonant High-Pass & Vactrol-Based Voltage Control

Support the channel: Complete project on falstad: (Note that the LDRs don’t react to light here – you can only change their resistances via the sliders.) My phone decided to unlearn proper white balancing at some point during filming. Sorry. Time to get a camera I guess. In this series, I’m taking a detailed look at how to build an analog VCF from scratch. Things get spicy this episode, as we begin to tackle the trickiest part of synthesizer circuit design: voltage control. If you want to follow along – which I strongly recommend –, here’s a bill of materials: 1x TL074 quad op amp 3x 5mm red LED 2x Light dependent resistor 1x 100k linear potentiometer 2x 100k resistor 3x 600 ohm resistor 2x 33 nF foil capacitor 1x Pack of FIMO Chapters: 0:00 Resonant High Pass 6:00 Voltage Control - Difficulties 9:04 Vactrol Basics 13:10 DIY Vactrols 16:03 Basic LED Driving 19:30 Offset Voltages & Voltage Mixing 22:38 Fixing the frequency range 26:50 Sound Demo & Outro