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LEHLE GmbH · Germany · www.lehle.com · [email protected]
HOW DOES AN EXPRESSION PEDAL WORK?
An expression pedal usually controls a
specific value of an effects device.
For example you want to use your foot
to control the mix amount of your delay
pedal.
In most cases your effects pedal offers a
control / potentiometer that cares about
the mix amount of your delay pedal. This
potentiometer will now be replaced by an
external expression pedal, that also usu-
ally works with a potentiometer.
The procedures, how this is being done,
are as complicated as they are varied.
Typically, your effects pedals send a volt-
age of 3.3 V or 5 V to the potentiom-
eter of the expression pedal. The poten-
tiometer as a variable resistor routes a
part of the voltage back. The sent back
voltage – also called control voltage – is
being changed by the position of the po-
tentiometer. The effects pedal measures
the control voltage and thus can modify
a parameter. In the above-mentioned ex-
ample the mix amount would be changed.
The individual cables and polarities in
summary:
RTS: the control voltage is being applied
to the ring of the TRS jack.
TRS: the control voltage is being applied
to the tip of the TRS jack.
TS: here the effects pedal measure the
voltage between sleeve and tip of the TS
jack.
Instead of stereo jacks or mono jacks we
are talking rightly about TRS and TS jacks.
!