Month: August 2025

I've been building trimless VCA units. The resources are available here: https://github.com/naokiiwakami/vca-unit/tree/v2 The simulation runs well. Tested the circuits on breadboard, went fine. Built a prototype on a 3" x 2" universal PCB, working fine. But the goal size is much smaller - 7/8" x 3/8". When I try a PCB of this size, a significant offset appears on output (0.4V to 1V, negative or positive) for zero input with -5V CV. This really puzzles me as all came from the same schematic. Such a large offset causes popping noises with steep CV attacks. I need to eliminate it. I'm building two types of VCAs in this project; NPN type…