The renowned Manley Stereo Variable Mu Limiter Compressor is a favorite of producers and recording engineers. Anyone who has heard the classic Fairchild 670 Series limiters in action has an idea of this Variable Mu's capabilities. Its adjustable attack and release settings are optimized for mixing and mastering, but are flexible for most tracking situations. Sonically versatile and dependable for daily use, the Variable Mu is Manley's best-selling device.
Classic compression/limiting
Although the Variable Mu is not a clone of one, the Fairchild 670 series used a similar limiting principle and those who are familiar with that piece of gear know this method to be very special. In fact, with mu meaning gain or amplification factor, the Variable Mu offers true variable gain, unlike most devices. How it works is that the unique 5670 dual trioide is at the center of the peak-reducing and compression action - and it's constantly being re-biased by the vacuum tube rectified side-chain control voltages. This causes the tube to smoothly change its gain.
The Varible Mu's Compress mode is soft-knee 1.5:1 ratio while the sharper knee Limit mode starts at 4:1 and moves to a more dramatic ratio of 20:1 when limiting over 12dB. Interestingly, the knee actually softens as more limiting is used. Distortion can be creatively used by turning up the Input and turning down the Outputs while using very little or no compression.
Perfect for dual-mono or stereo applications
You might notice that the Vari-Mu has a ganged input control, but it's certainly not mono-unfriendly. There are separate threshold and output controls to make compensations with, plus you can always adjust your individual source levels elsewhere. The advantage of the stereo input control becomes clear when you switch to Link mode, and that's what the Variable Mu does better than anything else: final mix, 2-track, or mastering limiting and compression.
The Mid/Side mod option opens the door to stereo encoding and decoding as well as exciting image enhancement processing capabilities. For instance, setting to compress only the in-phase information allows the augmentation of the stereo image as the out-of-phase content is left untouched. Or, conversely, if you need a more-mono mix for broadcast, or vinyl-cutting for instance, you can set it to kill off more of the out-of-phase info which leaves more in-phase material in the final result.
