Sognevo

Gjalla

gjalla, Old Norse: to shriek, to resound.

A free and open-source guitar amp simulator: a cheap transistor head, a distortion pedal in front of it and a cabinet that stops dead above 5 kHz, built with JUCE. Sibling of Galdr and Gala.

Download Source on GitHub

VST3CLAPAU (macOS)StandaloneWindowsmacOSLinux

The Gjalla GUI: a dark-fantasy themed guitar amp simulator interface
The GUI: dark-fantasy themed, resizable, with tooltips.

Download

Checking the latest release on GitHub…

Features

  • One chain from dry guitar to finished tone, in signal order: input trim, noise gate, pedal, preamp, tone stack, power section, presence, cabinet, frost, output trim
  • Noise gate on the clean signal ahead of every gain stage, with fixed 0.5 ms attack, 80 ms release and 4 dB of hysteresis, and no added latency
  • Three pedal voicings sharing one set of knobs: a cheap 90s distortion box, an HM-2 style chainsaw and a starved transistor fuzz (details in the table below)
  • Solid-state preamp: two cascaded gain-plus-waveshaper stages up to +36 dB, a sweepable 20-300 Hz tight filter ahead of the clipping, and a deliberate asymmetry that puts even harmonics in without leaving DC behind
  • Three-band tone stack plus a presence control after the power section
  • Three analytic cabinet voicings (4x12, practice combo, boombox), or load your own WAV/AIFF impulse response up to 2 seconds, or switch the cabinet off entirely for an external IR loader
  • Frost: a tilt filter at 1 kHz that takes the amp from dark to thin
  • 2x or 4x oversampling around the whole nonlinear path, 6 samples of latency (0.13 ms at 48 kHz) reported to the host and identical at both quality settings
  • Level compensation on the pedal and the preamp, so drive and gain buy distortion rather than volume and Master stays the volume control
  • Six factory presets, in/out level meters, right-click any knob to reset it or type a value, undo/redo (Ctrl+Z / Ctrl+Shift+Z)
  • Dark GUI shared with Galdr and Gala, resizable 0.75x to 2x, with tooltips on every control
  • Versioned session state: settings saved today keep loading in future versions
  • No telemetry, no network access, no update checks, no accounts

The pedal knobs

The pedal has three knobs and three voicings, and each knob means something different per voicing:

DistChainsawFuzz
Reference cheap 90s distortion box HM-2 style starved transistor fuzz
Drive 0 to +40 dB into an asymmetric diode clipper clip amount, 0 to +36 dB into a hard clipper 0 to +50 dB into a lopsided hard clipper
Tone tilt around 800 Hz, dark to thin sweeps the upper of the two pre-clip peaks, 700 Hz to 1.5 kHz post low-pass, 1 to 8 kHz
Level output trim, -12 to +12 dB output trim output trim

Dist high-passes at 60 Hz before clipping. Chainsaw pushes two fixed +9 dB peaks (250 Hz and the swept one) into the clipper and low-passes at 6 kHz afterwards, which is where the buzzsaw comes from. Fuzz clips harder on the positive rail than the negative one.

Installation

Extract the archive for your platform, copy each plugin into the folder below, then rescan your plugins in the DAW. The standalone app needs no installation and runs from wherever you put it.

FormatWindowsmacOSLinux
VST3 C:\Program Files\Common Files\VST3 ~/Library/Audio/Plug-Ins/VST3 ~/.vst3
CLAP C:\Program Files\Common Files\CLAP ~/Library/Audio/Plug-Ins/CLAP ~/.clap
AU n/a ~/Library/Audio/Plug-Ins/Components n/a
Standalone run directly run directly run directly

Building from source

You need git, CMake ≥ 3.22 and a C++20 compiler (Visual Studio 2022 on Windows, Xcode on macOS, GCC or Clang on Linux).

git clone --recurse-submodules https://github.com/andreademurtas/gjalla.git
cd gjalla
cmake -B build
cmake --build build --config Release

Builds end up in build/Gjalla_artefacts/Release/. On Linux, install the JUCE build dependencies first; the package list is in the README.

License

Gjalla is licensed under the GNU General Public License v3.0 or later. It is built on the JUCE framework (AGPLv3), uses the VST3 SDK interfaces distributed with JUCE (MIT), and clap-juce-extensions (MIT) for the CLAP build. Binary releases ship the relevant license texts in a licenses/ folder plus a NOTICE.txt with full attributions.

The GUI embeds UnifrakturMaguntia and IM Fell English, the same typefaces you are reading now, both under the SIL Open Font License.