Richard Atkinson

Web Audio MOS 6581 filter simulation

This is a Web Audio simulation of the MOS 6581 filter. It uses a wave shaper to simulate the distortion in the NMOS amplifiers in the SID chip. The fifth slider in the top row is the distortion amount.

Filter cutoff may be varied between 20 Hz - 20 kHz. Resonance may be varied up to 1000, which is an enormous value for any hardware resonant filter. This will distort the output of the Web Audio simulation, so to reduce the final output gain a Volume slider is provided (equivalent to register $18 in the SID). Filter modes are low pass, band pass, high pass, notch and all pass in the Web Audio simulation and the oscillator waveforms available are sine, triangle, sawtooth, square and pulse.

Global controls

Cutoff
Resonance
Filter mode
Volume
WaveShaperCurve

Oscillator one

Coarse tune
Fine tune
Waveform
Pulse width
Attack
Decay
Sustain
Release