7
USB 7706
C
ompressor Dual Channel
A
PPLICATIONS
I
n this section, several typical applications of the COMPRESSOR are discussed. The following basic settings can resolve
most dynamic problems. They are the ideal starting point. Please take the time to study the application examples care-
fully, in order to be able to make full use of the capabilities of your COMPRESSOR in the future.
1. MAIN APPLICATIONS AND INITIAL SETTINGS
T
he main applications of the COMPRESSOR can be divided into several categories:
a. The Expander/gate function is used to eliminate interference and to suppress background noise and leakage on indivi-
dual tracks in multi-track recording.
b. The Compressor function is used to compress the program material and to create special effects and unusual sounds,
which are used for recording and musical performance.
c. The Limiter function is designed to protect loudspeakers, tape recorders, transmitters, etc. from signal peaks, sort term
overloading and over modulation (transmitters etc.).
1.1 Compression! Leveling! Limiting/Clipping
Now that the functions and operation of the individual sections and their controls have been explained, we would like to
acquaint you with more of the terms and relationships of the dynamics process.
Compression
A compressor converts a large dynamic level into a restricted range. The extent of the resulting dynamic level is depen-
dent on the threshold, attack, release and ratio settings. As it is the desired effect of a compressor to increase a low level
signal, generally the threshold is set low. The "inaudible" compression mode requires fast attack and release times and
low ratios. The fastest the chosen control times and the higher the compression ratio, the greater the effect on the short-
term dynamics. This fact is often used to achieve audible and creative sound effects.
Leveling
The lev
eling mode is used to keep output level constant, i.e. to compensate for long term gain changes, without affec-
ting the short -term dynamics. Normally, the threshold is set quite low in order to be able to increase low-level signals.
Leveling requires slow attack and release times, combined with a high ratio. Because of the very slow response time, leve-
ling has no effect on signal peaks or short
-term changes in av
erage level.
Limiting
The limiting function requires a fast attack time and a high ratio and release time setting, which is dependent on the spe-
cific use and the desired sound effect. As it is usually the task of a limiter to limit only high signal peaks, the threshold is
usually set at a high level. The dynamics are reduced dependent on the ratio setting and the degree by which the thres-
hold point was exceeded. If the attack time is adjusted to control only the average level without affecting signal peaks
above the threshold, this is referred to as the program limiter. For this purpose the attack time will be set above 20 ms.
If the attack time is further reduced in order to also control signal peaks, this is defined as a peak limiter.
Clipping
In contrast to the two previously mentioned limiters, the clipping mode features infinitely fast control times, and infinite
compression r
atio and creates an unsurpassable barrier ("brick wall") for all signals above a certain level. To be able to
control the signal peaks, the clipping function radically cuts signals above the threshold, without affecting the amplitude
of the original signal. If used in normal applications, this function remains inaudible and under certain circumstances it
can even lead to an improved sound, because cutting the transients creates artificial harmonics. If misused, clipping can
cause very obvious and distasteful distortion, which when taken to the extreme, will con
v
ert the signal's w
aveform into
a square w
a
ve signal. This effect is often produced in guitar distortion devices ("fuzz boxes").
© US Blaster Europe BV
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