Subtractive Synthesis

Subtractive synthesis is a method of generating sound that removes frequencies from a generated waveform. Removal is done using filters and envelopes. The signals move through various modules until being output by your speakers. Pegboard, like many other synthesizers, uses this form of synthesis.

Signal generators. Pegboard includes two oscillators and one noise module. The PWM parameter changes the pulse width modulation of the square wave. It is disabled for the other two waveforms. The detune parameter adjusts the pitch in cents. Noise is mixed with the oscillators before proceeding on to the filter.

Filter. There are three filter types: LP 12, BP 12, and HP 12. These are a lowpass, bandpass, and highpass filter with a 12 db/octave slope. The Res parameter controls the resonance of the filter. The drive parameter amplifies the signal going into the filter. This can be used to add warmth or distortion to the sound.

Modulation sources. The synth includes two LFOs and two envelopes. They are used as modulation sources for other parameters in the synth. The first envelope is hard-wired to control the amplifier envelope of the signal. These signals can be routed by using the modulation matrix, as discussed in Modulation Matrix.

The envelope will pop if the attack or release is set too low. This causes the speaker cone to pop out because the ramp is set too steep. Usually this is undesirable, but it can be used as a transient for percussive sounds.