Eureka Microphone Preamplifier - Manual (Page 11)

CONTROLS & CONNECTIONS
11
Basically, as you turn the Threshold knob counter-clockwise, the input signal
is compressed. (If you have a ratio setting of greater than 1:1.)
RATIO: Sets the compression slope. This is defined as the output level
versus the input level. For example, if you have the Ratio set to 2:1, any
signal level above the Threshold setting will be compressed at a
compression ratio of 2:1. This simply means that that for every 1dB of level
increase into the compressor, the output will only increase ½ dB, thus
producing an attenuation of 0.5 dB.
ATTACK: Sets the speed at which the compressor ‘acts’ on the input signal.
A slow attack time (fully clockwise) allows the beginning envelope of a signal
(commonly referred to as the initial transient) to pass through the
compressor uncompressed, whereas a fast attack time (fully
counterclockwise) immediately subjects the signal to the Ratio and
Threshold settings of the compressor.
RELEASE: Sets the length of time the compressor takes to return the Gain
reduction back to zero (no gain reduction). Very short Release times can
produce a very choppy or ‘jittery’ sound, especially in low frequency
instruments such as bass guitar. Very long Release times can result in an
overly compressed signal, sometimes referred to as ‘squashing’ the sound.
All ranges of Release can be useful at different times however and you
should experiment to become familiar with the different sound possibilities.
(Refer to the applications section of this manual for some ideas.)
SOFT: selects Soft Knee and Hard Knee compression curves. When this
button is pushed in, Soft knee compression curves are used, otherwise hard
knee compression curves are used. With Hard knee compression, the gain
reduction applied to the signal occurs as soon as the signal exceeds the
level set by the threshold. With Soft knee compression, the onset of gain
reduction occurs gradually after the signal has exceeded the Threshold,
producing a more musical response (to some folks).