SM Pro Audio
Page 6 of 11
MBC502 manual
4
Optical Compressor
Why Optical Compression?
Optical compressors have a smooth gradual release curve making them pleasing to the ear, very
musical. This style of release is not usually found on a solid state or tube compressor. In simple
terms, the MBC502 optical compressor splits the signal between a sensor (resistor) and an LED
light. The light then acts as an attenuator on your volume path, controlling the amount of gain
reduction. The audio itself does not have any processing as such.
5
Channel controls
Controls for each channel are:
5.1
Level
The rotary knob control at the top of the MBC502 (labelled 0 to 10), controls the
amount of output level on each channel.
5.2
Mute
The white push buttons marked LOW MUTE & HIGH MUTE mutes the audio
signal for its respective channel. The corresponding LED with light up when the
channel is muted.
5.3
Rotary compression control
The (COMP) rotary compression control, sets the amount of compression. It
expresses the difference between the input level change and the output level
change. The higher the amount of compression, the smaller the dynamic range.
5.4
Rotary attack encoder
The (Att) rotary attack control allows for adjustment in milliseconds. Attack is the
time it takes the compressor module to respond to the corresponding input signal
before gain reduction occurs. Short attack times quickly bring down the level of
the loud, fast transients in the audio signal; long attack times let more sound
through before the compressor engages, resulting in a punchier sound.
5.5
Rotary release encoder
The (Rel) release control sets the time in seconds it takes for the compressor
module gain to return to the point of no gain reduction in the absence of audio
program material. Short release times create a more exaggerated effect
(“breathing”), whereas long release times have a more gradual decay.
5.6
Master Level
The Master Level VU Meter displays the audio level.
5.7
Gain Reduction Display
The GR display shows the amount of gain reduction on each channel.
5.8
Compression on/off switch
The white buttons under the GR LEDS are the channel compressor on/off
switches. Simply turns the compressor stage on or off for each channel.
