ER-301/Feedback Looper

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Applications

Description

Parameters

reset

Control Type Has Sub-chain? Sub-chain Parameters Behavior
Threshold yes threshold (-1 to 1) trigger


A rising edge at this parameter will cause the head to reset to the start position as set by the start parameter. Typically, the start parameter will be zero in which case the head will reset to the beginning of the buffer.

engage

Control Type Has Sub-chain? Sub-chain Parameters Behavior
Threshold yes threshold (-1 to 1) trigger or gate


The head advances forward when engaged and does not advance when it is not engaged. This parameter supports both momentary and latching behaviors. If the Engage Latch setting is 'on' then this setting behaves like a toggle such that a rising edge engages the head and the following rising edge disengages it. If the Engage Latch setting is 'off' then the head is only engaged while receiving a high value.

punch

Control Type Has Sub-chain? Sub-chain Parameters Behavior
Threshold yes threshold (-1 to 1) trigger or gate


This parameter is used to punch in or out when recording. It supports both momentary and latching behaviors. If the Punch Latch setting is 'on' then this setting behaves like a toggle such that a rising edge punches in and the following rising edge punches out. If the Punch Latch setting is 'off' then the unit is punched in only while this parameter is receiving a high value.

start

Control Type Has Sub-chain? Sub-chain Parameters Fader Scale
Gain/Bias yes gain (-10 to 10)

bias (-1 to 1)

linear


This parameter determines where in the loop buffer the head will reset. The position is proportional to the total buffer length so that 0 means the beginning of the buffer, 1 means the end, 0.5 means the middle, and so on. Negative values are supported and wrap around to the end of the buffer so that -0.25 is the same as 3/4 of the way into the buffer.

feedback

Control Type Has Sub-chain? Sub-chain Parameters Fader Scale
Gain/Bias yes gain (-10 to 10)

bias (0 to 1)

linear


This value determines how much of the original audio to keep when recording (i.e. punched in). A value of 1.0 means that the old and new are summed together as-is and will eventually cause the contents of the buffer to be so loud that it will clip when it arrives at the DAC. A value of 0.0 means that the new material completely replaces the old material. Anything less than 1.0 will cause the old material to slowly fade away with each recording pass. For example, suppose you set the feedback to 0.5 and then recorded a sine wave with amplitude of 1.0. After recording into the empty buffer, the sine wave will have an amplitude of 1.0 (= 0.5 x 0 + 1.0). Suppose for the 2nd pass you switch the input to silence and continue recording. After the 2nd pass, the amplitude of the sine wave will been attenuated to 0.5 (= 0.5 x 1.0 + 0.0). Continuing on this way, after the 3rd pass the amplitude will be 0.25 (= 0.5 x 0.5 + 0.0), then 0.125 and so on. The following graph summarizes the number of passes required to fade to 10% of the original recorded amplitude vs the feedback amount:

Time-to-fade.png

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 affects the cross-fade between the input signal and the playback signal in the output. A value of 1 (i.e. 100% wet) means you will only hear the contents of the buffer. 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:

Cross-fade.png

fade

Control Type Has Sub-chain? Fader Range Fader Scale
Simple Fader no 0 to 250ms linear time

The output might jump discontinuously when the play head loops at the beginning (ending) of the sample, or, when a trigger resets the play head position. When this happens, a fade is used smooth over the discontinuity in the output thus suppressing pops. This parameter sets the length of the fade used.

Pitfall.png
If you are using a single cycle wave sample to recreate a wavetable oscillator then it is recommended that you set this parameter to zero.