Alpha Juno style PWM Sawtooth with Analog Four.

Roland Alpha Juno

Roland Alpha Juno was released in 1985, and is a 6-note polyphonic synth with a single DCO. While regular synthesizers can pulse-modulate square waves, Alpha Juno can also apply pulse width modulation to sawtooth waves. This synthesis method differs from the Analog Four’s standard PWM sawtooth approach.

Play

Alpha Juno’s PWM sawtooth wave became famous for creating the iconic Hoover sound.

Analog Four Settings

• OSC1: TUN = 0, Wavform = Tri, PW = 64
• OSC2: TUN =12 , 24 or 36, Waveform = Pulse, LEV = 0, PW = 64
• OSC COMMON: AM1 = ON, Trig = ON E Oscillator Drift = OFF

The point of this synthesis method is that the frequency ratios of the two oscillators are integer multiples and the phases are synchronized.

Amplitude Modulation and PWM

Hoover sounds

Set the oscillators as configured above, enable unison mode, then apply pulse width modulation and pitch bending to complete the classic Hoover sound.

Demo Audio

01A4 Hoover Sounds1

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02A4 Hoover Sounds2

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A4 Mod Drum Patch Pack

The amplitude modulation and phase synchronization techniques demonstrated above are just one example of the creative possibilities explored in the A4 Mod Drum Patch Pack. This collection of 323 patches utilizes similar sound design approaches—combining oscillator sync, amplitude modulation, and harmonic relationships—to create a wide range of sounds including percussive tones, evolving textures, and FM-style voices.

A4 PWM Sawtooth - For Reference

Analog Four’s native PWM sawtooth wave is generated by rotating two identical waveforms in opposite directions. The overtones interfere with each other, creating a chorus or phaser-like effect.