Thermionic Culture THE PHOENIX Mastering Plus - Manual (Page 4)

©Thermionic Culture Ltd, August 2011 3
1 Introduction
The Phoenix is a stereo compressor, which can be used as
a pair of mono compressors. It has a ‘soft knee’ or ‘variable
mu’ characteristic in that the compression ratio increases
with the amount of compression being used. Initial
compression is 1.2:1 increasing to 5:1 at 15dB compression.
The Mastering PLUS Phoenix is the latest (2011/12) version
which combines all the best features of previous versions,
including all the gain available with the standard Phoenix so
as well as being an ideal stereo mastering compressor it can
be used for more extreme compression, with the advantage
of having faster operation. Other additions are the sidechain
filter, standby switch, and zero adjustment at the front.
The Mastering PLUS is easy to recall as it has all switched
controls (ELMA 24 position on the input), except for the
outputs, which are 31 position high quality indented pots for
finer level control. The zero level adjusters between the
meters control the current through the compression valves
and its important that the meters read zero when not
compressing. See section 2.
The sidechain works by filtering out bass frequencies from
the compressor's detector circuit and this makes the
compression less sensitive to the low frequencies present in
the audio signal.
It is due to the nature of bass frequencies that this is a
desirable effect. Bass frequencies tend to contain a lot of the
energy present in a full band signal and large fluctuations in
the amplitude of these frequencies can tend to dominate the
performance of the compressor.
A classic example is found when using a compressor over
the mix buss. If the music contains a bass instrument that is
not in all the way through the mix, it is noticeable that the
overall volume of the other instruments in the mix can go