Chameleon Labs 7720 Stereo Compressor - Used  From Chameleon

The 7720 Stereo Bus Compressor is perhaps our best achievement. High quality bus compression is a huge issue for mixers everywhere and the previous solutions were expensive. We started with a sonic target everyone is familiar with; the English console VCA compression system developed in the 80s. The heart of this console compression system was the dbx® VCA , designed by Les Tyler and now built by Les's company, THAT® Corporation.

The 7720's controls are set up as stereo device so that each control adjusts both channels. We included newer features, such as 5 switchable filters in the detector side chain: 60, 90, 130, 200 and 440Hz. This enables the user to custom tune the compressor behavior to prevent bass frequencies from triggering the compressor. In practice, this prevents the low end from dominating compressor activity. It makes a tremendous difference in the results! We also added a side chain input so that any input source can be the trigger for the compressor instead of the audio on the inputs of the unit. Metering of both input and output levels, on a VU meter, allows a fast and easy way to match the processed output gain of the unit compared to the input levels. From compression ratios as gentle as 1.5:1, to a more intense 10:1, the 7720 deserves to be across your final stereo bus.

Model 7720 Special Features

Meter switch:
The meter switch allows the meter to indicate either channels input level, either channels output level or the amount of stereo audio signal compression.

Sidechain:
This section modifies the control of the compressor with a mono audio signal introduced through the sidechain XLR input. A blue LED gives the user a visual indication that the circuit is active and that the sidechain audio is in control of the compressor, not the left and right audio inputs.

High Pass Filter:
The HPF rotary control allows the sidechain or main audio signal to be equalized to minimize lower frequency audio signals' effect on the compression character of the unit. The HPF affects the detection circuit, not the actual audio. The selector has six settings. The first setting does not introduce any filtration into the sidechain circuit. The next five settings are 60 Hz., 90 Hz., 130 Hz., 200 Hz. and 440 Hz. These selections allow a wide variety of choices. The high pass filter is designed so that the frequency selected is 3 dB down, with a roll-off of 12 dB per octave.

Ratio:
In addition to the ratio settings common to popular stereo compressors (2:1, 4:1, 10:1), the 7720 features a 1.5:1 setting. This allows the user to maintain control over the dynamics of the input signal without squashing the life out of the mix.

Non Stereo Application

In order to use the Model 7720 as mono compressor, you need only use the left channel inputs and outputs. All functions are as normal.

Power

External In-Line Power Supply : Each Model 7720 ships with an in-line power supply, type-dependent on country of operation. This is not a traditional "wall-wart" but simply an outboard AC transformer. DC filtering and regulation is accomplished inside the 7720 itself.