A guitar amp sim and multi-effects app.

Three amp slots, always running

Each slot plays a NAM capture (any amp-only .nam file) and stays running in the background, so switching between them is instant and click-free, from the panel or a MIDI footswitch (program change 1, 2, 3). Each slot is loudness-matched, calibrated to its capture's recorded input level, and has its own trims and tone controls.

Every slot comes with a built-in capture, clean, crunch, and high gain, so there's something to play the moment it opens. For now they're trained from BellyDSP's own amp model; captures of real amps will replace them.

A cab with mics you can move

Two close mics and a stereo room mic, each an impulse response with level, pan, polarity, delay, and mute, with automatic phase alignment and low and high cuts. Load a cab pack and drag a close mic across the speaker to morph between positions.

21 public-domain (CC0) cab IRs are built in, from a vintage and a modern 4x12. Load your own .wav IRs too.

Pre FX

• Gate before the amp and after it, linked, listening to the clean guitar signal, with adaptive release and a Learn button
• Compressor, in a studio and a pedal style
• Boost and overdrive, modelled from circuit schematics and oversampled, with several modes each
• EQ: a 9-band graphic or a 5-band parametric

Drag the blocks to reorder them.

Post FX

• EQ and compressor
• Harmonizer: up to four voices in key, reading the pitch from the clean guitar signal
• Multivoicer: up to eight voices for stacks and doubles
• Bloom: bitcrusher, phaser, and flanger in one block, in any order
• Chorus, delay (digital, analog, tape; stereo, ping-pong, dual; ducking), and reverb (room, hall, plate; freeze; shimmer)

Delay and reverb tails ring on when you switch them off. Drag to reorder.

Tuner, tempo, presets, scenes, MIDI

• A tuner with a needle on a ±50 cent scale, four tunings, A4 from 430 to 450 Hz, and a mute
• One tempo, tapped from the panel or a footswitch; delay, chorus, phaser, flanger, and reverb pre-delay can sync to it
• Presets with eight scenes each, undo and redo, A/B compare, and five factory presets
• Right-click any control to MIDI-learn a footswitch or an expression pedal; mappings save with the preset

A real-time audio engine

Zero added latency. The one exception is opt-in: the flanger's through-zero setting delays the signal by 5 ms while it's switched on, and says so. The audio thread never allocates memory, frees it, or waits on a lock, and an automated test checks that for every feature. With every block on, it uses about a quarter of the time a 128-sample buffer allows on the developer's Apple silicon Mac.

It runs at 48 kHz, the rate NAM captures are trained at.