About Compression
The dynamic range of a sound is the difference between its loudest and softest
points. For example, as you play your bass, youOll probably find that some
notes (for example, notes played on the upper frets of the lowest string) are
considerably louder than others. The function of the Compression circuitry in
the Model 5500 Bass Amplifier is to reduce overall dynamic range by automati-
cally reducing the level of the loudest sounds you play so that they are closer in
level to softer onesNthe end result is that the sound Oevens out� and all notes
played have pretty much the same level.
The front-panel Compression control determines the amount of compression
(peak signal reduction) by simultaneously adjusting both threshold and compres-
sion ratio (which ranges from 2:1 to infinity [limiting]). At the fully counterclock-
wise OOff� position, the circuitry is bypassed and no compression is applied (the
knob clicks when set to the OOff� position). As the knob is raised clockwise (at
settings from O1� to O �) increasing amounts of compression is applied. At the
highest settings, loud sounds will not just be compressed, but limited, where the
output remains virtually constant regardless of input.
The Model 5500 provides a front-panel Compression LED which acts as a use-
ful visual indicator of the continuous activity of the compression circuitry. When
lit steadily green (for example, when the Compression knob is set to OOff�), no
compression is being applied. When unlit, compression is being applied to the
546incoming signal at a ratio of approximately 2:1. When flashing red, the
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28compression ratio is approaching infinity (limiting is being applied). When lit
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0 steadily red, the signal is being limited. This LED Ofollows� the incoming signal,
changing continuously as different amounts of compression and/or limiting are
being applied.
HA5500
Compression control and LEDCompression has three main uses. First, as just described, it Oevens� out the
notes played by your bass so that they all appear at virtually equal level.
Second, it adds Opunch� to a sound; since all levels are nearly the same, you
can play with greater force without worrying about the loudest notes distorting.
Finally, it serves to protect your loudspeakers from damage as a result of brief
(transient) high output levels, as might be caused by finger-popping or other
performance techniques.
Whether or not you need to use compression with your Model 5500 will be a
matter of personal taste and playing styleNexperiment and see if you like the
effect. If you usually play at low volume levels, youOll find that, even with the
Compression knob turned up, the compression circuitry may have no audible
effect, so it might as well be off. In general, if you donOt need compression,
leave it off.
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ACEC
