12
About Compression
COMPRESSION
5
4
3
2
1
0
6
7
8
9
∞
VX3500
Compression control
and LED
The dynamic range of a sound is the difference between its loudest and softest
points. For example, as you play your bass, you’ll probably find that some notes
(for example, notes played on the upper frets of the lowest string) are consider-
ably louder than others. The function of the Compression circuitry in the Model
3500 Bass Amplifier is to reduce overall dynamic range by automatically reduc-
ing the level of the loudest sounds you play so that they are closer in level to
softer ones—the end result is that the sound “evens 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 “Off” position, the circuitry is bypassed and no compression is applied (the
knob clicks when set to the “Off” position). As the knob is raised clockwise (at
settings from “1” to “
∞
”) 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 3500 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 “Off”), no
compression is being applied. When unlit, compression is being applied to the
incoming signal at a ratio of approximately 2:1. When flashing red, the
compression ratio is approaching infinity (limiting is being applied). When lit
steadily red, the signal is being limited. This LED “follows” the incoming signal,
changing continuously as different amounts of compression and/or limiting are
being applied.
Compression has three main uses. First, as just described, it “evens” out the
notes played by your bass so that they all appear at virtually equal level.
Second, it adds “punch” 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 3500 will be a
matter of personal taste and playing style—experiment and see if you like the
effect. If you usually play at low volume levels, you’ll 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 don’t need compression,
leave it off.
