Aurora Audio GTC2 - Manual (Page 4)

The seven illuminated switches are as follows :-
NB. The first item is with the switch off, the second with the switch on.
Bypass/In (Green switch) :- With the switch deselected, there is a hard (relay switched)
connection between the input and output XLRs. This also applies when the unit is
switched off/powered down and means that it could be left in a circuit path without
disturbing continuity.
When bypassed and the power is on, the VU meter and side chains are disabled to
prevent confusing meter information as the audio circuits would be all powered up.
When the button is pressed in, the hard bypass is released and the audio passes through
the unit. The VU meter should indicate the output level where 0VU = +4dBu = 1.228v
ac.
Side Chain Off/On (Red Switch) :- With the switch deselected the side chain is
disconnected from the audio path so that no compression takes place and all the audio
paths work at unity gain. As there are three alternative paths (described in detail later)
this offers ample opportunity to use their different sounding configurations to “sweeten”
or “modify” the sound passing through the compressor.
When the button is pressed in the side chain is activated and the degree of compression
will depend on the relationship between the input signal level, the value of the threshold
and ratio settings, and the mode of compression selected.
Opto/FET (Red Switch) :- The default control element is a photo-resistive opto
coupler whose degree of attenuation is controlled by a d.c. voltage generated by the side
chain. When the button is pressed, the opto path is switched out of circuit and replaced
by one using a FET (Field Effect Transistor) as the control element. Each element has a
particular sound footprint especially when compressing hard.
Output Level/Gain reduction (Yellow Switch) :- The VU meter default mode (switch
deselected) is the output level from the compressor. If the side chain is switched off and
the gain control set to 0dB this reading is also the input level to the compressor.
When the switch is pressed, the VU meter needle will rise to the 0VU point and will
then move backwards, towards the -20VU section of the dial, to indicate the dB's of gain
reduction being applied. As the opto compressor has a different attenuator characteristic
to the FET, you will notice a difference in gain reduction reading when switching from
opto to FET. This is to be expected.
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