Funnel Head

"In the Industry, you're what we call a Funnel Head"

This project implements a real-time guitar amplifier simulator VST plugin with a focus on harmonic distortion and cabinet emulation. The design combines wave-shaping, parallel filter processing, and impulse response convolution to replicate a guitar amplifier.

The plugin’s signal flow is encapsulated within a custom JUCE DSP processor class called Funnel. The audio input is first upsampled by a factor of 4 using the juce::dsp::Oversampling class, which handles the necessary low-pass filtering to prevent aliasing. A wave-shaping function is then applied, and the signal is upsampled again before a post-distortion gain is added.

The core of the distortion is the wave-shaping algorithm, which maps input values to output values. Two functions were explored: a custom exponential function and the hyperbolic tangent function (tanh). The final plugin utilizes tanh for its more reliable behavior. Both functions primarily generate odd harmonics, which were confirmed through FFT analysis.

The processed audio is then sent to a BandSplitter class, which separates the signal into two parallel processing chains using a Linkwitz-Riley crossover filter. This filter maintains a flat frequency response when the high and low bands are summed. Variable gain controls are applied to each band, and the signals are then recombined.

The plugin successfully simulates an amp with low latency. The multi-band EQ provides detailed tone shaping, and oversampling effectively prevents aliasing.