Voodoo Lab GCX Guitar Switcher - Manual (Page 8)

D I G I T A L M U S I C C O R P O R A T I O N 7
Audio Loops
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Important: GCX audio loops are for instrument and line level signals only. Using
them to switch amplifier or speaker outputs will severely damage your GCX.
The most important characteristic of an audio switcher is sonic transparency.
Some manufacturers implement loops using either optoFETs (optical
transistors) or LDRs (light dependent resistors), or a combination of the two.
Both optoFETs and LDRs cause sound coloration and measurable distortion.
Some even claim their switching to be passive while using optoFETs
(transistors are not passive). LDRs, while technically passive, are not linear
and therefore degrade tone quality.
The only completely transparent way to switch both instrument and line level
signals with no audible distortion is with relays. The GCX uses the finest gold
contact relays sealed in nitrogen. We also include a snubber circuit to improve
operation by filtering audio frequencies from the relay coil.
Great care has been taken to reduce the possibility of ground loops and hum.
GCX audio loop grounds are isolated, the return ground is lifted, and the
circuit board includes a noise reducing ground plane.
Effects Loops
The basic function of a GCX loop is to switch effects in and out of the signal
path.
In this example, when the loop is ON, the pedal is active. When the loop is
OFF, the pedal is bypassed.