RingMod

Version 1.1.1

A ring modulator audio plugin built with JUCE. Multiplies the input signal by a selectable carrier waveform to produce classic ring modulation sidebands, with a dry/wet mix control.

GUI prototype on Figma Community: https://www.figma.com/community/file/1657604575511164578

Parameters

Parameter	Range	Default	Description
Carrier Frequency	20 – 2000 Hz	440 Hz	Frequency of the carrier oscillator (log-scaled)
Dry/Wet Mix	0 – 1	1.0	0 = dry input only, 1 = fully ring-modulated output
Waveform	Sine / Saw / Square / Triangle	Sine	Shape of the carrier oscillator

View in Renoise

How It Works

Ring modulation multiplies the input signal by a carrier waveform:

output = dry + mix * (input × carrier − dry)

This creates sum and difference sidebands around the carrier frequency, producing metallic, bell-like, or robotic timbres depending on the carrier frequency, waveform, and input material.

Waveform character

Waveform	Character
Sine	Clean sidebands — classic ring mod sound
Saw	Dense harmonic stack; brighter and more aggressive
Square	Odd harmonics only; hollow, nasal timbre
Triangle	Softer than square; gentle odd-harmonic colour

Note: Saw and Square carriers contain harmonics above Nyquist that will alias at high carrier frequencies. This is an intentional DSP characteristic and adds to the character of those modes.

30 Hz UI Timer

The oscilloscope display is driven by a 30 Hz juce::Timer running on the message thread. It exists to solve a fundamental threading constraint in audio plug-ins.

The problem: two threads, no shared locks

processBlock() runs on the audio thread at real-time priority — it must never be blocked, stalled, or synchronised with a mutex. The UI (message) thread needs to display what the carrier oscillator is doing, but reading audio data from the UI thread directly would be a data race.

Solution: lock-free FIFO

processBlock() pushes carrier samples into a juce::AbstractFifo-backed ring buffer (scopeRing) on the audio thread. Every ~33 ms the timer pulls those samples out into the local displayBuf snapshot on the message thread. AbstractFifo is designed for exactly this one-producer / one-consumer pattern — no mutex needed.

Audio thread                   Message thread (30 Hz)
─────────────────              ──────────────────────────────
processBlock()                 timerCallback()
  │                              │
  ├─ generate carrier            ├─ drainScopeData() ──► shift displayBuf left
  └─ push to scopeRing (FIFO)    │                        append new samples
                                 └─ repaint() ──► paint() reads displayBuf

The rolling window is maintained by a shift-left / append-right memmove + memcpy strategy, so the oscilloscope always shows the most recent 512 carrier samples. The drain is capped to at most one frame's worth of samples (sampleRate / 30) so the displayed time window stays consistent across different host sample rates.

Why 30 Hz?

Concern	Detail
Smooth enough	30 fps is perceptually fluid for a waveform display
FIFO won't overflow	The FIFO holds ~185 ms at 44 100 Hz (kScopeFifoSize = 8192). At 30 Hz the timer drains every ~33 ms — well within budget
CPU headroom	60 Hz would double repaint cost for little visible gain on a slowly-changing oscilloscope

Building

Requirements

• CMake 3.22+
• A C++17 compiler (MSVC 2022, Clang, or GCC)
• Git (JUCE 8.0.13 is fetched automatically if no local copy is provided)

Configure and Build

# JUCE is downloaded automatically via FetchContent
cmake -B build
cmake --build build --config Release

To use a local JUCE tree instead (faster, avoids the download):

cmake -B build -DJUCE_PATH="/path/to/JUCE"
cmake --build build --config Release

The built plugin will be placed in build/RingMod_artefacts/Release/.

Supported formats: VST3, Standalone.

Installing into a DAW

Copy build/RingMod_artefacts/Release/VST3/RingMod.vst3 to:

OS	Default VST3 folder
Windows	C:\Program Files\Common Files\VST3\
macOS	/Library/Audio/Plug-Ins/VST3/

Auto-install after build (Windows, requires admin shell):

cmake -B build -DJUCE_PATH="..." -DCOPY_PLUGIN=ON
cmake --build build --config Release

MSI installer — download RingMod-v1.1.1-win64.msi from GitHub Releases for a one-click install to the system VST3 folder.

Ableton Live

Preferences → Plug-Ins → enable "Use VST3 Plug-In Custom Folder" or point it at the Common Files path above. Re-scan plug-ins after copying.

Renoise

Preferences → Plug-Ins/Devices → add the VST3 folder and click Re-scan. The plugin supports both mono and stereo FX tracks.

A self-contained example project is included at examples/sample_ringMod.xrns — open it directly in Renoise 3.5+ to hear the plugin in use (square wave bass, 342 Hz carrier, 29% wet mix).

Project Structure

ringmod/
├── CMakeLists.txt
├── README.md
├── LICENSE
├── assets/
│   ├── icon.svg
│   └── JUCE Plugin Development Overview.docx   # Reference doc for JUCE best practices
├── installer/
│   └── RingMod.wxs        # WiX v4 MSI installer definition
├── .github/workflows/
│   ├── compile.yml        # Build + MSI check on every push to master
│   ├── lint.yml           # cppcheck static analysis
│   └── release.yml        # Build + publish GitHub Release on v* tags
└── source/
    ├── PluginProcessor.h / .cpp   # DSP: phase accumulator, ring mod, state save/load
    ├── PluginEditor.h / .cpp      # GUI: custom knobs, oscilloscope, waveform selector
    └── GUI.png                    # Reference screenshot

Changelog

1.1.2

• Applied JUCE best-practice improvements (no behavioural change for end users):
  • Standalone settings file moved from the working directory to %APPDATA%\RingMod\ringmod.ini (reliable cross-DAW path)
  • processBlock now guards against hosts delivering blocks larger than samplesPerBlock via jassert + jmin
  • All std::atomic<float>::load() calls on the audio thread now use std::memory_order_relaxed
  • AudioParameterFloat / AudioParameterChoice updated to the juce::ParameterID { id, version } constructor (JUCE 7+ form)
  • Replaced JUCE_IGNORE_VST3_MISMATCHED_PARAMETER_ID_WARNING with the semantically correct JUCE_VST3_CAN_REPLACE_VST2=0
  • resized() now stores column bounds as member variables; paint() reads them directly instead of recomputing the layout geometry
  • Oscilloscope FIFO drain capped to sampleRate / 30 samples per frame for consistent time-scale across sample rates
  • ComboBox waveform items now populated dynamically from the AudioParameterChoice choices list
  • Added JUCE Plugin Development Overview reference document to assets/

1.1.1

• Reworked the GUI to match the Futuristic Audio Filter Figma reference: synced mix progress-bar, footer status bar with parameter pips, corner accents, scanline overlay, and richer background glow
• Fixed CI: dropped the pinned CMake Visual Studio generator so builds auto-detect the toolset actually installed on the runner image

1.1.0

• Added Waveform parameter: Sine, Saw, Square, Triangle carrier shapes
• Replaced juce::dsp::Oscillator with a direct phase accumulator for allocation-free waveform switching on the audio thread
• Waveform switches only at phase zero-crossing to avoid mid-cycle discontinuities
• Added isBusesLayoutSupported — plugin now accepts mono and stereo FX tracks (Ableton Live, Renoise)
• Added processBlockBypassed for click-free DAW bypass
• Added WiX v4 MSI installer; releases published automatically to GitHub Releases on version tags

1.0.0

• Initial release: sine carrier ring modulator, dry/wet mix, oscilloscope, custom knob UI

License

MIT — see LICENSE.