Phaser

• Effect
• Since 0.2.0
• modulation
• sweep
• notch
• allpass
• stereo

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Phaser sweeps a set of notches up and down the spectrum, the classic whooshing, swirling sound of a chain of allpass filters mixed back with the dry signal.

What it does#

Each channel runs through 2 to 12 first-order allpass stages that share one break frequency. An allpass passes every frequency at full level but delays its phase; mixed with the dry sound, the two cancel wherever the chain has shifted the phase by an odd multiple of half a cycle. That gives one notch for every two stages. A sine sweep moves the break frequency between Low and High, either at Rate or locked to the shared transport when Beats is above zero. Feedback sends the last stage back into the first, deepening the notches and raising peaks between them. Channel spread offsets the sweep for each channel, so a stereo signal swirls between the speakers.

The stages are normalized lattice allpasses: a sweeping coefficient never adds energy, so even fast sweeps with high feedback stay clean, and the engine reports a proven tail for every setting.

When to use it#

Use it on pads, guitars, electric pianos, drums and noise for movement without the pitch wobble of Chorus. For a single static notch or band use State-variable filter; for echoes use Delay.

Ports#

Parameters#

Stages (stages)#

How many allpass stages are in the chain: 2, 4, 6, 8 or 12. Every two stages add one notch, so 4 stages give the familiar two-notch phaser and 12 give six notches.

Rate (rate_hz)#

Sweep cycles per second, from 0.01 to 20 Hz, when beats is 0.

Beats (beats)#

Beats per sweep cycle, phase-locked to the shared transport: 4 sweeps once a bar in 4/4 and always lands on the same point of the bar. At 0 the sweep runs freely at rate_hz. While the transport is stopped a synced sweep holds still.

Depth (depth)#

How much of the range from low_hz to high_hz the sweep covers, around its geometric centre. At 0 the notches stay put at the centre.

Low (low_hz)#

The break frequency at the bottom of the sweep.

High (high_hz)#

The break frequency at the top of the sweep. It is kept below 45 % of the sample rate.

Feedback (feedback)#

Signed gain from the last stage back into the first, from -0.95 to 0.95. Positive values deepen the notches and add resonant peaks between them; negative values move the peaks and make the notches shallower.

Channel spread (spread)#

How the sweep phase is distributed across channels. At 0 every channel sweeps together; at 0.5 a stereo pair is a quarter cycle apart; at 1 the channels are spaced evenly around the cycle.

Mix (mix)#

Dry and wet blend. 0.5 cancels fully at the notches; 1 is the allpassed signal alone, which sounds like a subtle phase shift on its own.

Tips#

• Slow rates (0.1 to 0.5 Hz) with 4 stages are the classic phaser; 12 stages with high feedback sound more like a jet.
• Keep low_hz above a few hundred hertz on bass-heavy sounds to keep the low end steady.
• Long tails at high feedback and very low break frequencies are real: the notches ring as they decay.

See also#

Chorus, State-variable filter, Delay.

Help patches

Each help patch is an ordinary Toy that teaches one idea. The diagram shows the Patch; the preview shows its Frame. Open it in TuneToys to play and edit it.

1. Sweep a phaser

beginner Teaches: rate_hz, depth, low_hz, high_hz, mix

A saw wave swept by a four-stage phaser.

Connections as text

• Oscillator audio output connected to Phaser audio input
• Phaser audio output connected to Patch outputs audio input

• A bright, steady saw gives the notches plenty to cut into.
• Rate sets the sweep speed; Low, High and Depth set where the two notches travel.

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2. Stages, feedback and spread

intermediate Teaches: stages, feedback, spread

A double saw through a phaser with selectable stages and resonant feedback.

Connections as text

• Oscillator audio output connected to Phaser audio input
• Phaser audio output connected to Patch outputs audio input

• Every two stages add one notch: 12 stages cut six notches at once.
• Feedback sharpens the sweep; Channel spread moves left and right apart.

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3. Lock the sweep to the beat

advanced Teaches: beats

A plucked loop whose phaser sweep follows the shared transport.

Connections as text

• Oscillator audio output connected to Envelope audio input
• Envelope audio output connected to Phaser audio input
• Phaser audio output connected to Patch outputs audio input

• Beats above zero lock one sweep cycle to that many transport beats.
• At 0 the sweep runs freely at Rate instead; a stopped transport holds a synced sweep still.

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Related nodes

• Chorus Prepared multi-voice chorus, ensemble and vibrato over arbitrary channel bundles.
• Filter Low-pass, high-pass, band-pass, notch, all-pass or morphing filter with resonance, 12/24 dB slopes, curve editing and output RTA.
• Delay Tempo-aware, smoothly retimed echoes with colored, ducked and explicit multichannel feedback.