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Manley Variable Mu Stereo Compressor Limiter

Dual-channel Tube Limiter/Compressor with Stereo Link and True Variable Gain
$4,999.00

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Manley Variable Mu Stereo Compressor Limiter
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True Variable Mu Limiting and Compression

The renowned Manley Stereo Variable Mu 2-channel limiter/compressor is a favorite of producers and recording engineers — and one listen to what this remarkable all-tube, transformer-coupled device does for your sound will make you a believer, too! Anyone who has heard the classic Fairchild 670 limiter in action has an inkling of the Variable Mu’s capabilities, but the sound is even sweeter with the Variable Mu. Its adjustable threshold, attack, and release settings are ideal for tracking, mixing, and mastering; while its highpass sidechain gives you added flexibility. The Manley Variable Mu is a high-end, esoteric piece of kit that delivers miraculous results on individual tracks, stems, and full stereo mixes. It’s also incredibly versatile and rock-solid reliable for daily use. A modern all-American legend, the Variable Mu fortifies your mixes with glue and punch, crystallizing them into professional, radio-ready product that blasts right out of the speakers. Add one to your studio rack, and hear what you’ve been missing!

A modern all-American legend

Although the Variable Mu is not a clone of one, the Fairchild 670 series used a similar operational principle and engineers at Sweetwater who have used that legendary unit know this method to be very special. With “mu” meaning gain or amplification factor, the Variable Mu offers true variable gain, unlike most compressor/limiters. How it works is that the 5670 dual triode is at the core of the peak-reduction action as it is constantly re-biased by the tube-rectified sidechain control voltages. This causes the tube to smoothly change its gain, and is responsible for the Variable Mu’s unique and highly effective gain reduction behavior, which gives you maximum level control with minimal artifacts.

From light leveling to heavy limiting

The Variable Mu’s Compress mode is a 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 employed by turning up the Input and dialing down the Outputs while using very little or no compression.

Perfect for dual-mono or stereo applications

You might notice that the Variable Mu has a ganged input control, but it’s certainly not mono-unfriendly. There are separate threshold, attack, release, 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 where the Variable Mu excels — on stereo buses and for mastering your final mixes. As one reviewer put it: It’s like pouring “sweet cream” over your mix!

Manley Variable Mu Compressor/Limiter Features:

  • Manley input and output transformers with pure nickel laminations in mu-metal case
  • Flat frequency response from 20Hz–25kHz
  • Balanced Inputs and Outputs
  • Fully differential all-tube circuitry using one 5751, 7044, and 12AL5 per channel
  • Variable Gain vacuum tube (per channel): 5670
  • 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
  • Variable Attack: 25msec–70msec
  • Continuously variable Threshold
  • Switch for Limit or Compress modes
  • Front-panel mounted Meter calibration
  • Limit (4:1 to 20:1) or Compress (1.5:1)
  • Large Illuminated Sifam Meters
  • Stereo Link switch
  • Handcrafted in Chino, CA

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Tech Specs

  • Number of Channels: Stereo, 2-channel
  • 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

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Customer Reviews

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Rated 5/5

The Best Compressor I've Ever Used

My recording background was collecting hand-me-down gear from friends and The Recycler through the '90s (one friend gave me four Roland S-760s for free!). Writing/recording was always my passion but not my job. I was a session guitarist and did record through iconic gear but never put my hands on them. Then the home computer plug-in craze came and I was hooked for about fifteen years. My ears weren't good enough to know the difference. Neither were my clients because I did begin a career as a composer who did his own engineering and mixing. About 5 years in, my computer broke down and to hit a deadline, I dusted off my old reel-to-reel machine and Lexicon PCM-90. I was shocked at how much better it sounded than my digital platform. That became the birth of my true ears: hearing depth. Next came the decision to pay $ for a microphone (U87). Couldn't be worth it, right? Well, it was. Made mixing 20 times easier. It already tracked with the sound I was looking for. Forward to 2023 Black Friday. Even though I use an analog 500 series master comp, I dug deep and bought the Manley. Wow! I A/B'd my 500 series and the Manley. It sounded like a completely different mix. Stereo definition was massive. And the depth, even deeper. Sheen like I've only heard on an SSL board. There's truly no bad setting on this thing. Even floored sounds usable. So my lesson: If you can afford it, Go big. Get the tried and true classics. You won't regret it.
Music background: Composer/Producer/Studio Owner
Rated 5/5

Manley Varu Mu use in a UK legendary studio convinced me to get one

I had no opinion about the Manley Varu Mu Limiter/Compressor (mastering version) until I went to Abbey Road Studios and had their mastering experts use it in conjunction with their legendary Fairchild 670s. These legendary mastering engineers (I will not name) used it quite extensively during my mastering sessions. I got a first-hand master class on how to use this piece of gear. It has it's own feel and responds very much like their Fairchilds.

...What is good enough for Abbey Road Studios is good enough for me.
Music background: Producer, composer, movie soundtrack composer, conductor, recording engineer.
Rated 5/5

Amazing tune mastering!

When I got this product, I was mainly planning on just getting my mix as loud possible for cd. My mix sounded incredibly louder and more pleasing to my ears. With plug ins, i tend to lose the drums if the limiting was too much. The Vari Mu made it easy to maintain my mix and get the volume I wanted.
Music background: Music producer/ Artist
Rated 5/5

It’s magic

Years ago, I was introduced to this wonderful piece of kit at a studio I was hired to play keys. I had no knowledge of what a Manley Vari Mu was. The projects singer started singing some Jackson Brown to show off. I can remember the expression on the drummers face as we looked at each other with amazement. We couldn"t believe the sound coming out of the tiny little genelecs and a sub. Then we were let in on this secret sauce machine. It turned into the single most important piece of gear I"ve lusted after for years.
Rated 5/5

Look, you just need this!

Like many landmark moments in a person's life, I remember the first time I heard a Vari-Mu. It was right around the turn of the century and a studio client brought one in to my humble little 48-track analog studio with his favorite preamps and mics. We had one of those well-known British consoles with a built-in buss compressor (really, not a bad one at all). You know the one, with the clunky automation. LOL. So the client says, "hey can we bypass that buss compressor and insert my Manley Vari-Mu on the stereo mix instead?"

I'd been mixing music for about 15 years at this point and I thought I'd heard it all. Wow, was I wrong! Immediately on first listendown, it was like I had reached Nirvana (the metaphysical state, not the band). Everything in the mix just became "better." The highs were elevated in the most musical luscious way, I'd ever heard, the mids were pushed out front and center with an immediacy and a "snap" that just reached out of the speakers and gently caressed your eardrum, and the lows pushed me back in my chair, becoming the bold anchor of each track. Everything sit perfectly where it belonged, where I had *intended* it to belong, almost as if the Vari-Mu was reading my musical mind and it knew just what to do. There's only one way to describe that: Magic. Pure magic.

Sell your car if you have to, but buy one of these. Buy it now.
Music background: Mixer, Engineer, Occasional corporate executive.

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What Do Our In-house Gear Experts Think?

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.

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.

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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