# ER-301/Doppler Delay

## Applications

For further details on applications, see ER-301/Delay.
• Tape-like delay effects such as warble.
• High quality audio rate modulation of delay time for FM-like effects.

## Description

This is a fully interpolated delay line in which the speed of the read head tracks changes in the delay value at the full sample rate. An accurate analogy would be to imagine grabbing the play head of a tape loop player and moving it closer to (or further from) the record head. Since this is an interpolated delay line, sub-sample delay times are supported.

This delay is called a Doppler Delay because it is equivalent to a digital simulation of the Doppler effect where the air between the listener and the sound source is acting just like a delay line. If the listener (or sound source) moves away then this is the same as lengthening the delay line (increasing delay) and the pitch will be lower while they are moving away from each other. If the listener (or sound source) moves closer then the delay line is effectively shortening and the pitch will be higher while they are moving closer to each other.

### Maximum Delay Time

This menu setting allows you to expand (or shrink) the pre-allocated buffer for the delay line. The size of this pre-allocated buffer determines the maximum delay time accessible in real-time via the delay parameter.

Delay units are created with a default buffer length of 1s.

## Parameters

### delay

 Control Type Has Sub-chain? Sub-chain Parameters Fader Scale Gain/Bias yes gain (-3 to 3) bias (0s to Ns) linear time

This parameter dictates the length of the delay line. In other words, how long it takes for a sound to pass from the input to the output of the Delay unit. The maximum value of this parameter (N) is determined by the Maximum Delay Time setting in the unit's menu.

When this unit is placed in a stereo chain, then the delay parameter is split into separate parameters for the left and right channels.

### feedback

 Control Type Has Sub-chain? Sub-chain Parameters Fader Scale Gain/Bias yes gain (-3 to 3) bias (${\displaystyle -\infty }$, -36dB to 0dB) logarithmic

This value determines how much of the audio in the delay line to mix with the delay's input. A value of 0dB means that the old and new are summed together as-is and will eventually cause the contents of the delay line to grow so loud that it will clip when it arrives at the DAC. A value of ${\displaystyle -\infty }$ means that the new material completely replaces the old material in the delay line. Anything less than 0dB will cause the old material to slowly fade away with each (delayed) repeat. The following graph summarizes the number of repeats required to fade to 10% of the original captured amplitude vs the feedback amount:

### wet

 Control Type Has Sub-chain? Sub-chain Parameters Fader Scale Gain/Bias yes gain (-3 to 3) bias (0 to 1) linear

This parameter controls the amount of the input signal and of the affected signal which is passed to the output. A value of 1 (i.e. 100% wet) means you will only hear the affected signal. A value of 0 (i.e. 100% dry) means you will only hear the signal received at the unit's input. However, the cross-fade curve is not linear but rather lifted to counteract the tendency for loudness to dip in the center of a linear cross-fade curve. The actual cross-fade curve looks like this: