Aurora Audio GTQC - Manual (Page 4)

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 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 (Green 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.
Any electrical meter is always more accurate at the full scale deflection end of the scale so small
mechanical and electrical discrepancies (around 2dB) may apply in the -20dB region. (i.e ±10%
accuracy)
Auto Release Off/On (Green Switch) :- If the switch is deselected the attack and release times are set by
the two blue potentiometers. The user should always experiment with the settings of these controls to see
how they affect the sound.
When the Auto button is pressed the release time is dependent on the nature of the program material
passing through the compressor. Generally the release times are longer but, if the material is short bursts
of sound, the auto timing capacitor will have less stored energy and will produce shorter release times. If
the material is long, flowing, rifts then the capacitor will charge up more and produce longer release times.
The actual timing value changing constantly with the nature of the material passing through the
compressor.
Combined Off/On (Blue Switch) :- When deselected the control element is either the opto or FET path
4