Manley Stereo Variable MU Compressor

The Manley Stereo Variable MU Compressor has been Manley’s top-selling product for many years. It stands as one of the rare compressors that has established itself as a true standard in mastering studios, contributing to most hit records of the past decade and likely the next.

“Mu” is tube terminology for gain, and Variable Mu® is Manley’s trademarked term for this limiter compressor. Its operation involves the “remote cut-off” or re-biasing of a vacuum tube to achieve compression.

This technique, also utilised by the coveted vintage Fairchild 670, sets it apart as one of the few all-tube compressors known to do so. Even the sidechain features glowing rectifier tubes. So, how does it function?

At the heart of its peak-reducing and compression action lies the unique 5670 dual triode, constantly re-biased by the vacuum tube rectified side-chain control voltages, inducing smooth gain changes in the tube.

In COMPRESS mode, it offers a soft-knee 1.5 to 1 ratio, while the sharper knee LIMIT mode begins at 4 to 1 and escalates to a more aggressive ratio of 20 to 1 when limiting over 12dB. Notably, the knee softens with increased limiting.

Distortion can be creatively manipulated by boosting the Input and reducing the Output, even with minimal or no compression applied. The gain reduction curves provide a visual representation of this effect.

Although the Manley Stereo Variable MU Compressor features a ganged input control, it is not restricted to mono applications. Feel free to track away! Separate threshold and output controls allow for adjustments, and individual source levels can be fine-tuned elsewhere.

The stereo input control truly shines in LINK mode, showcasing the Manley Stereo Variable MU Compressor’s prowess in final mix, 2-track, or mastering limiting and compression.

As one reviewer aptly described the Manley Stereo Variable MU Compressor, “It’s like pouring a bowl of sweet cream over the mix.” Deliciously satisfying. So, go ahead and envelop your music in its embrace.