The DBX 266 Compressor/Gate is an audio processor used for music and broadcast applications. In practical use, compressors provide dynamic control of volume levels by increasing softer sounds and limiting peak levels of louder sounds. Gating helps reduce source background and audio system noise when sound is not present. DBX 266 inputs are connected to sound source outputs including musical instruments, sound mixers and music players. Compressor outputs connect to load devices such as sound system power amps, instrument amplifiers, recording devices or additional sound processing equipment. Instructions assume mono operation of the 266 with DBX recommended compression settings for audio system overload protection and gate settings for controlling background noise.
Connecting the DBX 266 Compressor
Turn off the power to the DBX 266 and all equipment to be connected.
Place the DBX 266 near equipment to be connected. It may be mounted in a standard 19-inch equipment rack or placed on a flat, stable surface.
Insert the 1/4-inch instrument cable plug into the main output jack of the source device and insert the remaining plug into the DBX 266 "Channel 1" input jack on the rear panel.
Insert the second instrument cable plug into the compressor's "Channel 1" output jack and insert the remaining plug into the main input jack of the load or amplification device.
Set the compressor's channel one "Output Gain" control to the lowest "minus 20" setting.
Plug the DBX 266 AC power adapter mini plug into the 18-volt AC power jack on the back of the unit and plug the power transformer into a standard electrical outlet.
Turn on the power switches of the compressor and all connected equipment.
Depress the "Stereo Couple" button to the outward position for mono operation. The red LED light will illuminate if "Stereo Couple" is active. In mono mode, Channel 1 and Channel 2 control sections operate independently. In "Stereo Couple" mode, Channel 2 controls are disabled -- except for the "Gain Reduction" control -- allowing Channel 1 controls to be used for both stereo channels.
Using the DBX 266 Compressor Section
Turn the "Threshold" control knob to "10." "Threshold" dictates when compression is applied in relation to the incoming signal volume and may be adjusted to a low of minus 40 decibels to a high of 20 decibels. Green or red LEDs illuminate when respective threshold levels are below or above input level range. An amber LED illuminates when DBX's patented "Over Easy" compression effect is active at higher threshold and ratio levels. Compression takes place only when the input level is within or beyond the threshold setting.
Turn the "Ratio" control knob fully to the right. This setting is marked as the symbol for "infinity" followed by the ratio setting of ":1." "Ratio" controls the amount of compression effect applied to the input signal when the threshold level is reached, and can be adjusted from a low of 1:1 for no compression to infinity :1 for maximum compression.
Turn the "Attack" control knob fully to the left in the "Fast" range. "Attack" controls the point in which compression is applied to the input signal. "Fast" ranges allow compression to take effect quickly, while "Slow" ranges allow compression to appear gradually as input volume approaches the threshold setting.
Turn the "Release" control knob to the left, approximately one notch above the lowest "Fast" setting. "Release" controls the point in which the compression effect is no longer active and can be set from "Fast" for rapid compression cutoff to "Slow" for gradual compression cutoff.
Set all source and load device volume and tone settings to normal operating levels.
Emit sound from the source device while turning the "Gain" control knob up until the target volume is obtained.
Using the DBX 266 Expander/Gate Section
Turn the Expander/Gate "Threshold" control knob to approximately "negative 35." "Threshold" adjusts the level at which the input signal is audible and is adjustable from "Off" to 10 dB for maximum gating.
Turn the "Expander/Gate Ratio" control knob to the right at approximately three o'clock. "Ratio" controls the input signal cutoff point as it decreases in volume and can be adjusted from minimum to maximum levels. Lower ratios allow gradual audio volume decay while higher settings allow abrupt volume cutoffs.
Experiment with different compressor and expander/gate controls to obtain the desired results. There are no definitive settings, as operation of the DBX 266 and similar devices are wholly dependent on input source types, volume levels and the desired effect.
Exaggerate the usage of compression or gate functions to add sustain qualities of stringed instruments and prevent overtones of percussion instruments.
Stereo operation or connection of two distinct mono source outputs and load inputs are connected in the same manner with two additional instrument cables and manipulation of the "Stereo Couple" switch, as described in Section 1, Step 8.
Do not connect the power amp or instrument amp speaker outputs to the compressor as severe damage will result.