ER-301/Dub Looper

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Applications

Description

The Dub Looper combines the input audio with the audio in its buffer like this:

Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://en.wikipedia.org/api/rest_v1/":): {\displaystyle \begin{align} \mbox{NEW} &= (\mbox{dub}) \mbox{INPUT} + (1-\mbox{dub}) \mbox{OLD} \\ \mbox{OUTPUT} &= \mbox{XFADE}(NEW,INPUT;\mbox{wet}) \end{align} }

where,

  • INPUT = the unit input
  • OUTPUT = the unit output
  • OLD = the previous contents of the buffer
  • NEW = the new contents of the buffer
  • XFADE(x,y; 0% to 100%) = the crossfade of x and y

In contrast to the Feedback Looper (which can have greater than unity gain), the Dub Looper always has unit gain. Here are some concrete examples,

  • 0% dub means that the existing buffer contents are kept untouched.
  • 25% dub means that 25% of the input signal is mixed with 75% of the existing buffer contents.
  • 100% dub means that the input completely overwrites the old buffer contents.
  • 0% wet means that you only hear the input of the looper and none of the buffer contents.
  • 100% wet means that you only hear the output of the looper and none of its input signal.

The crossfade curve (denoted XFADE in the formula above) is lifted to compensate for the dip in output volume that results when you use a linear crossfade curve.

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.

dub

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

bias (0 to 1)

linear

This parameter determines how much of the input signal should be mixed with the existing buffer contents while keeping a total unity gain. A dub of 1 (or 100%) means that the input signal completely replaces the existing buffer contents while a dub of 0 (or 0%) leaves the existing buffer contents untouched. A 25% dub will mix 25% of the input signal with 75% of the existing buffer.

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.