Allpass Filter Node

Standard allpass filter, lets all frequencies through, but changes the phase-relationship between the various frequencies.

How to Use

The Allpass Filter Node needs a source audio signal connected to its audio input, to which it can apply the effect, and then output the result. The input audio signal can come from anywhere, as long as it's audible: an Audio File Node, Oscillator Node, Noise Generator Node all work. Click their output, then click the audio input of the Allpass Filter Node to establish a connection.

Connect to an Audio Destination Node to listen to the output, and play your project if your audio source needs it.


Audio Input

An audio signal to filter. You can also connect a control signal, but results will vary based on whether the control signal changes in a way that conveys meaningful frequency information, or not.

Frequency-Control Input

A control signal to control the Frequency setting. You can also connect an audio signal, but keep in mind that it can cause the Allpass Filter Node to become unstable and reset. See the technical details section below.

You can enable this input from node properties, or by connecting to it.

Sharpness-Control Input

A control signal to control the Sharpness setting.

You can enable this input from node properties, or by connecting to it.



The frequency with the maximal group delay (where the center of the phase transition occurs), in Hz.


Controls how sharp the transition is at the center frequency. The larger this value is, the sharper the transition will be.

Filter Order

The order of the differential equation describing the filter. In simpler terms, when you increase the filter order, it’s essentially the same as chaining multiple Allpass Filter Nodes.


Audio Output

The filtered audio or control signal (depending in input).

Technical details

The Allpass Filter Node is a digital biquad filter, and as such, it's possible for it to become unstable, e.g. in response to rapid frequency modulation. When this happens, the Allpass Filter Node will attempt to reset itself every few seconds, to avoid remaining unstable forever. This auto-reset is done in real-time mode (i.e. when you play your project), but not during exporting. That is, if the filter becomes unstable while exporting, it may remain unstable until the end of the exported audio.

Note: the behavior of this auto-reset is mostly non-deterministic, and depends on several undocumented factors. Don't rely on it to produce "glitchy" audio. Instead, use a Gain Node with an LFO-controlled gain, or a similar amplitude modulation technique.

Node conversions

★ With AudioNodes HD

Node conversion is available from the node menu.

Convert to: Notch Filter Node

When converting, FrequencyFilter Order and Sharpness values are transferred to the new Notch Filter Node

Convert to: Bandpass Filter Node

All the values from above are transferred to the new Bandpass Filter Node