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Rosso
Hear your guitar pedal before you solder it.
Draw a schematic and it makes sound on the spot. Lotus Engine, a circuit solver written in Rust, solves real circuits built from 1,920 real parts - from germanium fuzz to tube preamps. Free for Windows and macOS.
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.
About Rosso on Product Hunt
“Hear your guitar pedal before you solder it.”
Rosso was submitted on Product Hunt and earned 0 upvotes and 1 comments, placing #11 on the daily leaderboard. Draw a schematic and it makes sound on the spot. Lotus Engine, a circuit solver written in Rust, solves real circuits built from 1,920 real parts - from germanium fuzz to tube preamps. Free for Windows and macOS.
On the analytics side, Rosso competes within Design Tools, Accessories, GitHub and Audio — topics that collectively have 310.2k followers on Product Hunt. The dashboard above tracks how Rosso performed against the three products that launched closest to it on the same day.
Who hunted Rosso?
Rosso was hunted by Tsukuba Acoustics. A “hunter” on Product Hunt is the community member who submits a product to the platform — uploading the images, the link, and tagging the makers behind it. Hunters typically write the first comment explaining why a product is worth attention, and their followers are notified the moment they post. Around 79% of featured launches on Product Hunt are self-hunted by their makers, but a well-known hunter still acts as a signal of quality to the rest of the community. See the full all-time top hunters leaderboard to discover who is shaping the Product Hunt ecosystem.
For a complete overview of Rosso including community comment highlights and product details, visit the product overview.
Tsukuba Acoustics