Manley Variable Mu

Dual-channel Tube Limiter/Compressor with Stereo Link and True Variable Gain
Manley Variable Mu image 1
Manley Variable Mu image 1
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Manley Variable Mu
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True Variable Mu Limiting and Compression!

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/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.

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 th 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 response
  • 20Hz-25KHz frequency response
  • Balanced Inputs & Outputs
  • Fully differential all-tube circuitry using one each 5670, 5751, 7044, & 12AL5 per channel
  • Independently regulated B+ and Heater supplies
  • Includes HP Sidechain modification as standard
  • Hard-wire Bypass switch
  • Silent conductive plastic input attenuator
  • Recovery 5 steps: 0.2s, 0.4s, 0.6s, 4sec., 8sec. (Not a 12-step recovery)
  • Variable Attack: 25msec-70msec
  • Continuously variable Threshold
  • Switch for Limit or Compress modes
  • Front panel mounted Meter Adjust
  • Limit (4:1 to 20:1) or Compress (1.5:1)
  • Large Illuminated Sifam Meters
  • Stereo Link Switch
  • Maximum gain: 35 dB
  • <0.1% THD @ 1KHz Noise floor: -85dB typical
  • Max. output +30dBm (26Vrms) 26dB Headroom
  • Power consumption (120/240VAC): 80 watts
  • Dimensions: 19" x 3 1/2" x 10" (occupies 2U)
  • Shipping weight: 23 lbs.
Add the perfect compression with Manley's Variable Mu!

Additional Media

Signal Processing Buying Guide
Plug-ins vs. Hardware -- Which Should You Choose?
Manley Massive Passive EQ Variable Mu Demo by Mick Guzauski
Manley Variable Mu Review

Tech Specs

Number of Channels 2
Controls Recovery, Output, Threshold, Attack
Ratio LIMIT: (4:1 to 20:1) or COMPRESS: (1.5 to 1)
Frequency Response 20Hz-25KHz
Inputs 2 x XLR
Outputs 2 x XLR
Rack Spaces 2U
Height 3.5"
Depth 13.5"
Width 19"
Manufacturer Part Number MSLCHP

Customer Reviews

Based on 5 reviews
Write your review

Glue and warmth

Ed, my sales engineer, sold this unit to me, and I am grateful. This is such a beautiful piece of equipment. The dual input knob is great for dialing in the right amount of mojo on a mix. This unit can be used for heavy lifting or light compression. It can be clean or thick. It is an awesome compressor. Do not hesitate to pick one up.
Music background: Production

Earned it's reputation

Tracking, Mixing and Mastering the Vari-Mu is all over every project I've done over the last 12 years. From music to voice-over work, it's the one piece in my rack that gets used daily. Something always needs to be compressed and for me it's the first one I grab.
Music background: Recording Engineer, Producer, Musician

Manley Vari-Mu is Awesome

It helps me take my "in-the-box" mixes out of the box! I'm a long-time console guy and I never attempted finished, professional sounding mixes at home before, but my Vari-Mu is a big part of my ability to do so. The sonic qualities of my mixes have improved in a big way once I started using the Manley as a program compressor. I little goes a long way and I love this thing! It's a Manley... it's going to sound great!
Music background: 30+ years as engineer, producer, educator, & musician

Perfect box

Essential to my studio. Perfect for recording, mixing and mastering. Can't recommend it enough!
Music background: Producer/Engineer/Mixer

A Modern Classic!

I don`t own the Vari Mu but I have had the extreme pleasure of working with it. This is the desert island compressor we all would want. Just one listen and you`ll know why. The Vari Mu works beautifully on the overall mix but it really shines on anything. What impresses me the most about this box is how much you don`t hear it. Its so good you will swear its not working but you know it sounds better. The first time I used it I pretty much slammed the ratio as hard as I could just to hear some compression. The ratio was something like 20:1. I know its insane but thats my point!
Music background: Singer-Songwriter-Producer

Sweetwater Advice

Brendan Murphy

This is a great smooth compressor. Try it on a 2-bus or with a pair of drum overheads... it's not like any other compessor you own.

Jeff Hollman

The Vari-Mu is a modern classic, and for good reason! I love that way it sounds on the master bus of a mix... the compression helps to glue the mix together and makes everything sound "finished." With three tubes and two transformers per channel, nothing quite sounds as good to me on a rock or pop mix like a Manley Vari-Mu.

Gilbert Janke

The Manley VariMu is an American success! It's hand-built right here on U.S. soil, and sought after the world over. When handling the unit, you can immediately tell it was built and intended to last to give you years of phenomenal service, without needing to be serviced like its vintage counterparts. Simply put, it is a wildly successful and highly used magic machine. It's great for tracking and mastering because of how clean and open it can sound, but when strapped across your stereo 2 buss it gives you a unique sonic footprint, leaving your mixes tighter, more defined and polished. At higher compression it produces that loved and pleasing harmonic distortion without adding too much coloration, but still delivers the goods even when just kissed with your audio signal. Many compare it to the "holy grail" of compressors, the Fairchild 660/670, and after pushing some program through it, it's more than obvious why studios the world over want this piece in their racks!
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See also: Compressors, Manley, Manley Compressors / Limiters, Manley Compressors / Limiters