MKAudio

A C++ library for high-performance audio signal processing, focusing on analog modeling techniques optimized for real-time applications.

Overview

MKAudio explores two complementary approaches to analog audio modeling:

1. Numeric Modeling - Lightweight saturation approximation using mathematical functions
2. Circuit Simulation - Real-time transient analysis of actual circuit schematics

Both approaches are designed for low memory footprint and minimal computational overhead, making them suitable for real-time audio processing.

Modules

Saturation (Numeric Modeling)

The saturation module implements a novel approach to modeling analog saturation characteristics without circuit simulation or impulse responses. The core idea is to use logarithmic functions (log2) with carefully tuned parameters to approximate the nonlinear transfer functions found in analog equipment.

The model supports:

• Asymmetric saturation - Independent control over positive and negative signal portions via separate alpha (drive/knee) parameters
• Compression control - Beta parameters for adjusting gain/compression characteristics on each polarity
• DC bias - Delta parameter shifts the saturation curve's center point
• Polarity flip - Optional signal inversion

This approach can be chained: saturation stage → filter → saturation stage → filter, building complex analog-style processing chains while maintaining efficiency.

Key files: saturation.h, saturation.cpp

Circuit Simulation (Real-Time Transient Analysis)

The simulation module provides authentic analog filtering by performing real-time transient analysis of circuit schematics. Audio signals are treated as source voltages, and the circuit response is computed sample-by-sample using Modified Nodal Analysis (MNA).

Features:

• Component library - Resistors, capacitors, and inductors with companion model discretization
• Templated circuit engine - Compile-time fixed sizes (NumDevices, NumNodes) for maximum performance
• Gaussian elimination solver - Optimized linear system solver with partial pivoting
• Preprocessing step - Static admittance matrix (Y) is built once before audio processing
• Per-sample processing - Dynamic current sources updated each sample for reactive components

This enables modeling of actual analog filter topologies (RC filters, LC networks, etc.) with physically accurate frequency response and transient behavior.

Key files: simulation.h, simulation.cpp

Building

mkdir build && cd build
cmake ..
cmake --build .

Requires CMake 3.22+ and a C++17 compatible compiler.

Usage

Saturation

#include "saturation.h"

// Create saturation with asymmetric parameters
MKAudio::Saturation sat(
    10.0,   // alphaPlus (positive drive)
    8.0,    // alphaMinus (negative drive)
    1.0,    // betaPlus (positive compression)
    1.0,    // betaMinus (negative compression)
    0.0,    // deltaBias
    false   // flipPolarity
);

double output = sat.process(inputSample);

Circuit Simulation

#include "simulation.h"

// Create circuit: 4 devices max, 3 nodes max
MKAudio::Circuit<4, 3> circuit(44100.0);

// Build an RC lowpass filter
circuit.addComponent(std::make_shared<MKAudio::Resistor>(1, 2, 1000.0));   // 1k ohm
circuit.addComponent(std::make_shared<MKAudio::Capacitor>(2, 0, 1e-7));    // 100nF

// Preprocess (call once before audio starts)
circuit.preprocess(0.1);  // source impedance

// Process audio
double output = circuit.process(inputVoltage, 2);  // probe node 2

License

This library is dual-licensed:

GPL-3.0 for open source projects

Commercial license available for closed source usage

For commercial licensing inquiries, contact: minjaekim@mkaudio.company