Quadcomp ®
II
Owner's Manual v 4.0 CE ©2010 ARX®
Quadcomp ®
II
Owner's Manual v 4.0 CE ©2010 ARX®
4
5
Application Notes - Compressors and Limiters
A
compressor
is a variable gain amplifier whose output voltage compared to input voltage
decreases as its input level increases past a set threshold.
A
limiter
is essentially a compressor with a high compression ratio, thus maintaining an
essentially constant output level despite any increase in input level past the threshold.
So, let’s look at this in non-technical terms. Basically, what this type of device does is keep an
eye (or ear?) on signal levels, stopping them from getting any louder than the level you set
(the Threshold). A compressor puts a gentle ‘squeeze’ on the excess level, whereas a limiter
hits excess level on the head with a hammer!
Each channel of the Quadcomp
II
can act as either compressor or limiter, since its Ratio
control is infinitely variable, from 1:1 right through to oo:1. So you can have low compression
(1.5:1 to 3:1), medium compression (3:1 to 6:1), heavy compression (6:1 to 10:1) and limiting
(10:1 to oo:1). These numbers refer to the amount of input signal in dB that will produce an
increase of 1 dB at the output.
A lot of compressor/limiters use some form of peak detection, with response characteristics
that are definitely audible. However, each channel of the Quadcomp II features a true RMS
detector that closely follows the response of the human ear to level changes, making it as
natural sounding as possible while still retaining full audio control. Plus, the ARX ‘Auto Soft’
TM
circuitry gives soft knee transfer characteristics at low to medium compression, changing to
hard knee around 8:1. This gives virtually inaudible subtle compression where needed, but
maximum output before limiting when used as an overall level controller.
Front Panel Controls
• Hardwire bypass compressor IN/OUT switch.
• Numbered marker panel for labelling compressor assigns. Use a grease pencil, Chinagraph
or something similar. Please don’t use a felt tip marker as these may permanently stain the
panel.
• Threshold control. This varies the level at which the compressor will start to modify the
signal dynamics. Variable from -40dB to +20 dB.
• 7 segment LED display Gain Reduction meter; from 0dB to -24dB.
• Ratio control. This determines how much the signal is compressed when it reaches the
Threshold. It is totally variable from 1:1 to infinity:1.
• Output gain. Variable from -20dB to +20dB.
Rear Panel Connectors
• Balanced XLR Input socket. Pin 3 –, Pin 2 +, Pin 1 Ground
• Sidechain Insert TRS socket. Tip IN, Ring OUT, Sleeve GROUND
• Balanced XLR Output socket (wiring same as Input)
• Stereo link switches for Channels 1 and 2, 3 and 4 Master/Slave configuration.
When switched IN, Channels 1 and 3 are the Masters and control all functions except
Output gain. When switched OUT, all four Quadcomp channels are totally independent.
• IEC 3 pin AC connector and integral fuseholder. Replace fuse with correct value only: 100
- 120 V AC 1 amp, 220-240 V AC 0.5 amp. Please also refer to voltage details on Page 2
