HTekDistortion Plugin

Description

A piecewise, memoryless soft-knee hard clipper, where the knee transition is implemented by smoothstep interpolation between linear and saturated regions, with optional bias and baseline subtraction (DC compensation).

Drive (driveDb)

Higher drive pushes more signal into the knee/clip region, thus gives more distortion and loudness (unless compensated).

preHPF

High-pass filter cutoff (StateVariableTPTFilter highpass) that runs before the waveshaper. User has the ability to remove low frequencies before clipping so bass doesn't dominate the distortion.

Threshold (threshold)

Sets the clip ceiling. Increasing threshold allows higher peaks through, often louder and less saturated.

Knee (knee)

Controls the width of the knee region around the threshold. Knee uses smoothstep interpolation between linear and clipped output. If knee is zero we have a very hard clip behavior (more harsh highs/aliasing). With a higher knee we have a smoother transition and softer distortion character.

Bias (bias)

Adds a DC offset before shaping: waveshape(x + b, ...). Creates even harmonics and a more "dirty" tone breaking the odd-symmetric property of the transfer curve.

postLPF

Low-pass filter cutoff (StateVariableTPTFilter lowpass) that runs after the waveshaper (and after mix). Removes high harmonics created by clipping and can remove hissing sounds that come from high frequencies, resulting in a less fizzy distortion.

Mix (mix)

Wet/dry blend between the current sample (dry) and waveshaped sample (y). Mix=0 yields the filtered clean path (preHPF then postLPF). Mix=1 yields fully distorted (then postLPF).

Output (outputDb)

Applied to the distorted (wet) signal after waveshaping (before mix) for level trim.

Oversampling (pending)

Should be used to reduce aliasing artifacts introduced by the nonlinearity by processing at a higher sample rate and filtering before downsampling (pending).

Signal flow from input to output

Here we assume that the entire processing graph in the DAW contains only the HTekDistortion plugin.

Distortion Algorithm

Waveshapers

Before VS After Waveshaping

Spectrum Before VS After Waveshaping

HTEKDistortionEffect::process(block)

Configure Libraries

• JUCE_LIB

  The project supports local JUCE checkout (via JUCE_LIB) or automatic fetching using CMake FetchContent (if environment variable JUCE_LIB is not set).

  If you want to set the environment variable execute:

  Windows (Powershell)

  Temporary:

  $env:JUCE_LIB="\absolute\path\to\JUCE"
  

  Persistent:

  setx JUCE_LIB "\absolute\path\to\JUCE"
  

  Linux / macOS

  Temporary (current shell session only):

  export JUCE_LIB="/absolute/path/to/JUCE"
  

  Persistent (add to ~/.bashrc, ~/.zshrc, etc):

  echo 'export JUCE_LIB="/absolute/path/to/JUCE"' >> ~/.bashrc
  source ~/.bashrc
  

  Define the environment variable JUCE_LIB to reference the JUCE source root directory (the directory containing CMakeLists.txt and modules/).

  If you use a different environment variable name in your build system, replace JUCE_LIB in CMakeLists.txt accordingly with your defined environment variable name. JUCE modules are statically linked into the plugin for easy distribution, thus object code is embedded into your plugin binary. But, the plugin itself is a dynamic library.

  Using the same logic you can setup your environment variable CATCH2_LIB to be able to run the tests in effects/tests.

• CATCH2_LIB

  CATCH2_LIB must point to the Catch2 source root (contains CMakeLists.txt).

  Windows (PowerShell)

  Temporary:

  $env:CATCH2_LIB="\absolute\path\to\Catch2"
  

  Persistent:

  setx CATCH2_LIB "\absolute\path\to\Catch2"
  

  Linux / macOS

  Temporary:

  export CATCH2_LIB="/absolute/path/to/Catch2"
  

  Persistent (add to ~/.bashrc, ~/.zshrc, etc):

  echo 'export CATCH2_LIB="/absolute/path/to/Catch2"' >> ~/.bashrc
  source ~/.bashrc
  

Windows (GUI):

Alternatively, define JUCE_LIB and CATCH2_LIB as User Environment Variables in Environment Variables (View Advanced System Settings -> Environment Variables).

Downloads

• JUCE repository: https://github.com/juce-framework/JUCE

• Catch2 repository: https://github.com/catchorg/Catch2

• CMake source and binary distributions: https://cmake.org/download/

• Note: As we will see in the next section, one can choose not to build with tests and have the plugin only. Tests are here for assuring the quality of the development process.

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Build Project

You can build the plugin in Debug or Release mode. In your project root directory execute:

• Debug

  Windows (Visual Studio / multi-config)

  cmake -B build 
  cmake --build build --config Debug
  

  Windows (Ninja / single-config)

  cmake -B build -G Ninja -DCMAKE_BUILD_TYPE=Debug
  cmake --build build
  

  macOS (Xcode / multi-config)

  cmake -B build -G Xcode
  cmake --build build --config Debug
  

  Linux/macOS (Ninja/Makefiles / single-config)

  cmake -B build -DCMAKE_BUILD_TYPE=Debug
  cmake --build build
  

• Release

  Windows (Visual Studio / multi-config)

  cmake -B build 
  cmake --build build --config Release
  

  Windows (Ninja / single-config)

  cmake -B build -G Ninja -DCMAKE_BUILD_TYPE=Release
  cmake --build build
  

  macOS (Xcode / multi-config)

  cmake -B build -G Xcode
  cmake --build build --config Release
  

  Linux/macOS (Ninja/Makefiles / single-config)

  cmake -B build -DCMAKE_BUILD_TYPE=Release
  cmake --build build
  

Plugin artefacts are under build/plugin/*_artefacts/*/VST3/....

Build with tests

If you want to build with tests, then execute:

cmake -B build -DBUILD_TESTS=ON

before cmake --build <build_folder> .

Test binary will be under build/effects/tests/ (.../Debug/HTekEffectsTests.exe on Windows).

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