Here's some background on the Manley Variable Mu compressor:The renowned Manley Stereo Variable Mu compressor/limiter is a favorite of producers and recording engineers - and one listen to what this device does for your sound will make you a believer, too! Anyone who has heard the classic Fairchild 670 Series limiters in action has an idea of this Variable Mu's capabilities - but the sound is even sweeter with the Variable Mu. 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.Manley Variable Mu Compressor/Limiter at a Glance:- Classic compression/limiting- Ranges from light leveling to heavy limiting- Perfect for dual mono or stereo applications- Classic compression/limitingAlthough 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 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.Ranges from light leveling to heavy limiting: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. Like one reviewer put it: "It's like pouring a bowl of sweet cream over the mix."Manley Variable Mu Compressor/Limiter Features:Manley input & output transformers with pure nickel laminations in mu-metal case with flat frequency response20Hz-25KHz frequency responseBalanced Inputs & OutputsFully differential all-tube circuitryIndependently regulated B+ and Heater suppliesIncludes HP Sidechain modification as standardHard-wire Bypass switchSilent conductive plastic input attenuatorRecovery 5 steps: 0.2s, 0.4s, 0.6s, 4sec., 8sec. (Not a 12-step recovery)Variable Attack: 25msec-70msecContinuously variable ThresholdSwitch for Limit or Compress modesFront panel mounted Meter AdjustLimit (4:1 to 20:1) or Compress (1.5:1)Large Illuminated Sifam MetersStereo Link SwitchMaximum gain: 35 dB<0.1% THD @ 1KHz Noise floor: -85dB typicalMax. output +30dBm (26Vrms) 26dB HeadroomPower consumption (120/240VAC): 80 wattsDimensions: 19" x 3 1/2" x 10" (occupies 2U)Shipping weight: 23 lbs.Add the perfect compression with Manley's Variable Mu!