Pr
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v3 P
rofes
sional E
ffects Mix
er with USB
ProFXv3 Professional Effects Mixer with USB
12
For hybrid channels (mic input and stereo
line input), the gain control just affects
the microphone input.
Hybrid Channels:
• ProFX6v3 – Channels 3/4 (no gain knob)
• ProFX10v3 – Channels 5/6 – 7/8 (no gain knobs)
• ProFX12v3 – Channels 5/6 – 9/10
• ProFX16v3 – Channels 9/10 – 13/14
• ProFX22v3 – Channels 15/16 – 19/20
• ProFX30v3 – Channels 23/24 – 27/28
The gain control on the 1/8" stereo input
channel has 20 dB of gain and 20 dB
of attenuation.
1/8" Stereo Channels:
• ProFX6v3 – Channels 5/6 (no gain knob)
• ProFX10v3 – Channels 9/10 (no gain knobs)
• ProFX12v3 – Channels 11/12
• ProFX16v3 – Channels 15/16
• ProFX22v3 – Channels 21/22
• ProFX30v3 – Channels 29/30
Next to every gain knob – except the 1/8" stereo input
gain knob – lies a level set LED. These LEDs are used
with the gain control to set the channel preamplifier
gain just right for each source. If one or more channels
are distorting, check the level set LEDs. If they are on
continuously, turn down the gain.
14. Compressor Knobs
The following channels of each ProFXv3 mixer has
an in-line compressor circuit with a variable threshold.
• ProFX6v3 – No compressor knobs
• ProFX10v3 – Channels 1 – 2
• ProFX12v3 – Channels 1 – 4
• ProFX16v3 – Channels 1 – 8
• ProFX22v3 – Channels 1 – 12
• ProFX30v3 – Channels 1 – 16
This is very useful for compression of vocals,
and snare drums, for example, so you might consider
connecting your vocal and drum mics to these
channels, rather than one of the other channels.
When the incoming signal exceeds the threshold
level set by this knob, the signal level is automatically
compressed. This reduces the dynamic range and
reduces the chance of distortion due to overloading
the input signals.
Dynamic range is the difference in level
between the quietest and loudest parts of a
song. A compressor “squeezes” the dynamic
range, resulting in an overall steadier, more
constant volume level for the signal. It helps sources,
such as vocals, “sit” properly in the mix; it is very useful
for live sound.
The compression ratio is fixed at around 6:1, with a
soft knee response. The threshold can be adjusted
clockwise from off (no compression) to 0 dBu (max).
As an example, suppose the threshold is set to
maximum. An incoming signal reaches the threshold of
0 dBu. As it increases beyond the threshold, it becomes
compressed at a ratio of 6:1. This means that even if
the input further increases by 6 dB, the actual output
only increases by 1 dB. This compresses the output
signal, so 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 above 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).
1 My High School math teacher, Mr. Marvin, thought that graphs might come
in handy for me one day. Finally!
+20
-10
-5
+0
+5
+10
+15
+20
-10
-5
+0
SLOPE 6:1
SOF
T KN
EE
SLO
PE
1:1
+5
+10
+15
INPUT SIGNAL STRENGTH dBu
OUTPUT SIGNAL STRENGTH dBu
GAIN
U
+60
MIC
GAIN
