What does a dynamic processor do?
• They make very subtle changes to a musical
• They inject depth, warmth and life into our mixes
and bring out the subtle nuances of the parts.
• They alter the range in volume between the
loudest and softest sound on a recording or
amplified musical performance.
There are four main types of
VCA (voltage control amplifier)
Depending on the volume of sound the VCA can
be set to bring up or down the volume of signal.
A VCA acts like someone who constantly
controlling the fader on a mixing board for one
particular sound. If a sound is too loud they turn
it down, if a sound is too soft they turn it up. The
advantage to a VCA is that it can act much faster
and precisely than any human being and it can
control the volume of several sounds
Dynamic Processors are generally
patched in two ways:
• directly to the instrument
• using the channel insert on a mixing board
COMPRESSORS & LIMITERS
• Compressors and limiters are designed to turn
the loudest part of a signal down.
• When the VCA senses that a signal is exceeding a
certain level it acts on the signal and turns it
• A compressor is almost always used on vocals,
bass and on instruments with wide dynamic
There are three main functions that
• they protect against overly loud sounds that can
overdrive electronic circuitry and cause unwanted
• they even out sounds in the mix that tend to
constantly change volume.
• they increase the overall volume of the sounds
that we want in the mix thus improving the signal
to noise ratio.
There are four controls that are
common to all compressors/limiters:
ii) Attack Time
iii) Release Time
The threshold sets the volume (db) level at
which the compressor will begin to recognize
the signal. Once the signal surpasses this level
it’s fate is determined by the setting of the
other three dials. Therefore only sounds
above a certain volume level are altered.
ii) ATTACK TIME
The attack time controls the amount of time
that it takes for a compressor to turn down a
signal once it passes over the threshold. An
attack time that is set too fast will turn down
the transients causing certain important
elements of the sound to be lost. One that is
too slow will end up allowing unwanted
Attack time settings:
• On a vocal track we usually adjust the attack
time in order to make it high enough that the
S’s and T’s are heard but low enough that they
are not exaggerated.
• On a good compressor/limiter attack times
can be set anywhere between 100
microseconds and 20 milliseconds.
iii) RELEASE TIME
The release time sets the amount of time it
takes for the compressor to “let go” (or turn
the signal back up) once it falls below the
threshold. Release times can vary anywhere
between 5/100 of a second to as slow as two
or three seconds. Longer release times of one
second or more tend to produce the
smoothest and most natural results. This
varies depending on the tempo of the music.
• The ratio determines how much that a signal
is turned down. The ratio is the comparison
between the amount of signal that passes
over the threshold and the actual volume of
the signal that will be outputted from the
How is the dB output calculated?
Say that you set the compressors ratio at 3:1.
If a sound exceeds the threshold by
3 dB you will actually only hear the sound as
being 1dB above the threshold after it is
Solve the following question:
If you have a sound that is 12 dB above the
threshold with the 3:1 compression how loud
will it be outputted from the compressor?
The sound will be outputted at 4db above the
Most compressors have an LED or VU meter to
show how much gain reduction is taking place.
How are Limiters and Compressors
Both perform basically the same function. The
limiter is really just an extreme compressor. It
can compress signals at a 100:1 ratio.
• Compressors perform at ratios between 1:1
• Limiters perform at ratios from 10:1 and 100:1
EXPANDERS & GATES
• These are devices that are most commonly
used when mixing down a recording
• Although gates are frequently used by
musicians to eliminate noise in a live situation.
Expanders work in a similar way to a
compressor except they act on the signal that
is below a set threshold is instead of above a
Expanders are used to expand the dynamic
range of a piece of music.
Compressors make loud sounds softer.
Expanders make soft sounds softer
Upward Expanders ?
These days sound engineers are also making
increasing use of upward expanders (or
Volume Maximizers) in order to take loud
sounds and make them even louder !
A gate is an extreme version of an expander. They
are used most often to eliminate noise in a track.
Gates allow you to set a threshold that is just
above the noise floor. Any sound below the
threshold will be silent. Expanders are a little
more effective because they allow for sounds to
fade out a little more naturally. Gates sometimes
cause fading out sounds to get clipped
A summary of dynamic processors:
Dynamic processors are a very powerful and
essential tool in the studio. When used correctly they
will lead to clean, slick, smooth and professional
recordings. When used improperly they can lead to
annoying ,airy and noisy recordings . Learning to
properly use a dynamic proccesor is one of the most
poorly understood yet important skills in the modern
recording studio and live sound mixing.