Owner’
s Manual
15
Owner’s Manual
there is more protection to your system from distortion
and overload due to poor microphone technique (say
it ain't so) and general pops, bangs and heavy metal
screaming. The soft knee means that the compression
slowly ramps up to 6:1 from the threshold. It does not
jump abruptly to 6:1, as this would be hard knee
compression, and harder on the ears too.
The graph on the previous page shows the input signal
level going into the compressor, versus the output level
coming out of it. It is the typical graph to view when
compressors are discussed, and is just the kind of thing
our engineers like to discuss during the company
Christmas party
1
.
If the compressor is off, then the input = output. For
example an input signal level of +5 dBu results in an
output level of +5 dBu. The diagonal line from lower left
to upper right represents x = y, that is, input = output.
At the maximum compression, the threshold is
set at 0 dBu, and the input to output relationship
is represented by the lower curve. If the input is
–5 dBu (that is, below the threshold), the output
is –5 dBu. As the input reaches 0 dBu, the output
is a bit less than 0 dBu. If the input is +5 dBu, the
output is about +2 dBu. If the input r10 dBu,
then the output is +3 dBu. Notice the shapely curve
of the soft knee between the diagonal slope of x = y
and the compressor slope of 6:1 (the compression
ratio).
The other green curves represent in-between
positions of the compressor knob, with higher
thresholds before compression begins.
Outboard compressors often have controls such as
compression ratio, threshold, soft knee/hard knee,
attack time, and release time. These last two affect how
quickly the compressor kicks in when the input exceeds
the threshold, and how quickly it is released after it
drops below the threshold. In this compressor, these
parameters are specially chosen to give you the best
overall performance.
Adjust the threshold carefully, so your dynamic range
is still lovely, without distortion or overload during the
performance. Run through a few practice screams and
high-notes, and adjust the compression as required.
1
My High School math teacher, Mr. Marvin, thought that
graphs might come in handy for me one day. Finally!
27
26
27. USB Switch
[ProFX16v2, ProFX22v2, ProFX30v2]
The USB switch on the last stereo channel provides
stereo playback of iTunes
®
, or a DAW via the USB
connection. Like any other input, this signal may
also be EQ'd, sent to an aux bus, or mixed in with
the other signals and assigned to subgroups or main
outs. This switch overrides the TRS inputs.
