Hi Product Hunt 👋 I'm a solo developer from Japan. Rosso is a circuit simulator built specifically for people who make guitar pedals. The idea is simple: you draw a schematic on screen, press play, and the circuit is actually solved and turned into audio in real time. You can hear what changing one resistor does before you buy the part. What separates it from a general-purpose simulator is that Rosso doesn't use idealized components. Every part is a real part number carrying its own datasheet-derived behavior — 1,920 of them. Germanium transistors are graded by hFE and leakage current (180 of them), because in a Fuzz Face the transistor you picked *is* the sound. Tubes model grid current and blocking distortion. BBDs model per-stage charge transfer loss and clock-dependent bandwidth. The solver is written from scratch in Rust, so it runs in real time on an ordinary laptop. 14 circuits ship with it - Fuzz Face, BBD chorus, a 12AX7 preamp, a Marshall-style tone stack — so you can hear something within a minute of installing. Open the Fuzz Face and swap the transistor for a different part number. It changes. Two things to know before downloading: ・The macOS build is Apple Silicon only. ・The builds aren't code-signed. macOS may need `xattr -cr /Applications/Rosso.app`, and Windows will show a SmartScreen warning. Both are documented on the download page. It's free. What I'd most like is to hear where the models feel wrong - especially from anyone who has actually built these circuits.

Rosso

Hear your guitar pedal before you solder it.

Hear your guitar pedal before you solder it.