DL221 OPERATORS MANUAL
2
INTRODUCTION
The DL221 is a Dual Compressor/Limiter combining ease of operation with flexible
performance, low noise and low distortion. The DL120 is a Modular, Single
Compressor/Limiter offering identical performance.
Each section (Two in the DL221, one in the DL120) consists of a compressor, having
variable threshold, ratio, attack, release, and output gain, plus a separate peak limiter,
which is particularly useful in preventing momentary overload when using gentle
compression slopes and/ or slow attack times.
Although each section is completely independent, linking is easily accomplished, which
prevents image shifting when treating stereo material.
Particularly attractive features are the unique dual function displays using Tri-colour
LED’s, which measure input signal levels, or gain reduction.
Programme related, semi-automatic release characteristics make settings less critical
whilst dramatically reducing low-frequency distortion when using fast release times.
A compressor is a device which automatically controls the level of an incoming signal to
provide a more constant output.
Even in a digital system, which has a large dynamic range, compression is necessary on
some instruments and even on a final mix because the environment in which most
material is heard is often noisy, to say nothing of the limited dynamic range of the
reproduction equipment, e.g. portable radios and cassette players.
A well designed compressor should operate smoothly and create a minimum of distortion
and noise. Such a device in use should go almost un-noticed (unless for special effects)
and require a minimum of adjustment.
A limiter is essentially the same as a compressor but as its name implies, it serves to
prevent the output from rising any higher than a pre-determined level.
The use of compression effectively raises low level signals, but this includes any ambient
noise. For instance, vocals usually require compression, but noise from headphones,
together with the taking of breath, can be a problem for the engineer. This can be
overcome by the use of an expander, which will attenuate signals below a preset level,
i.e. the opposite of compression.
A device which performs all three functions gives all the benefits of compression and
limiting without the unwanted side effects. Additional refinements can greatly increase
the versatility of such a unit by automating some of the more critical control functions.
Equalisation may be applied to the compressor side-chain insert points. This allows
frequency conscious compression to be achieved. ‘Side chain listen’ facilities are
provided to allow both side-chains to be monitored.
