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Manley Stereo Variable Mu Limiter Compressor Certified Open Box , $4,499.10 - Add to Cart Skip to Product Information

Manley Stereo Variable Mu Limiter Compressor Certified Open Box

Dual-channel Tube Limiter/Compressor with Stereo Link and True Variable Gain
Manley Stereo Variable Mu Limiter Compressor
Manley Stereo Variable Mu Limiter Compressor

Certified Open Box Savings!

Save $499.90 What is Certified Open Box?

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Savings: $499.90 New for $4,999.00

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Manley Stereo Variable Mu Limiter Compressor Certified Open Box

Certified Open Box Savings!

Save $499.90 What is Certified Open Box?

The price below reflects your savings.

Savings: $499.90 New for $4,999.00

True Variable Mu Limiting and Compression

This article was Written By

Our Product Research Team

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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 Stereo Variable Mu Limiter Compressor 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
What is Certified Open Box Gear?

At Sweetwater, we're so picky that what we call "Certified Open Box" is actually better than what most music retailers sell as "new" gear! Our gear hasn't endured hundreds of people a week plunking away at all the keyboards, fumbling through Stairway to Heaven on every guitar or playing with every fader and knob on a mixer or control surface.

Certified Open Box (also known as a demo) means we’ve had it out of the box for our YouTube channel, displayed at events, tested in our studio, or maybe it was in a customer’s hands for a few days and isn’t ‘factory fresh’ as a result. Every Certified Open Box item we sell has Sweetwater’s 2-year Total Confidence Coverage™ warranty and has been tested and verified up to ‘new’ specs by our factory-authorized technicians to make sure it’s in perfect working order before we ship it to you.

When you buy a Certified Open Box item at Sweetwater, you get:
  • 2-year Total Confidence Coverage Warranty™!
  • Products inspected and tested by our factory-authorized techs, guaranteed to function like new (or better)!
  • FREE shipping on most items
  • Equipment that will MEET or EXCEED your expectations!

Click HERE to browse our current inventory of Certified Open Box equipment. Purchasing Certified Open Box gear from Sweetwater is a smart and safe way to save!

Warranty Info

Sweetwater's FREE 2-Year Total Confidence Coverage Warranty

Extra peace of mind at no extra cost.

  • Save money with FREE parts and labor
  • Get back to making music with the industry's fastest turnaround time
  • Fix it the first time with our award-winning, factory-certified Service Department
Learn More about Total Confidence Coverage

Offer applies only to single-receipt qualifying purchases. Select manufacturers may require that only the manufacturer’s products qualify towards the minimum purchase amount needed to be eligible for promotional financing. Otherwise, an invoice that meets the minimum purchase amount and contains at least one qualifying manufacturer product is eligible for promotional financing. No interest will be charged on promo purchase balance, and equal monthly payments are required on promo purchase until it is paid in full. The payments equal the amount financed divided by the number of months in the promo period, rounded up to the next whole dollar. These payments may be higher than the payments that would be required if this purchase was a non-promo purchase. During the last month(s) of the promo period the required monthly payment may be reduced due to the prior months’ rounding. Regular account terms apply to non-promo purchases. New Accounts as of 07/31/2025: Purchase APR is 34.99%. Penalty APR is 39.99%. Min Interest Charge is $2. Existing cardholders: See your credit card agreement terms. Subject to credit approval.

Offer applies only to single-receipt qualifying purchases. No interest will be charged on the promo balance if you pay it off, in full, within the promo period. If you do not, interest will be charged on the promo balance from the purchase date. The required minimum monthly payments may or may not pay off the promo balance before the end of the promo period, depending on purchase amount, promo length and payment allocation. Regular account terms apply to non-promo purchases and, after promo period ends, to the promo balance. New Accounts as of 07/31/2025: Purchase APR is 34.99%. Penalty APR is 39.99%. Min Interest Charge is $2. Existing cardholders: See your credit card agreement terms. Subject to credit approval.

The estimated required monthly payment shown which excludes taxes and delivery equals the amount financed divided by the number of months in the promo period, rounded up to the next cent. During the last month(s) of the promo period the required monthly payment may be reduced due to this rounding. These payments apply only with the financing offer shown. If you make these payments by the due date each month, you should pay off this amount financed within the promo period, if it is the only balance you are paying off. If you have other balances on your account, this payment will be added to any other minimum monthly payments.

Applies only to select items from this manufacturer. Ask your Sweetwater Sales Engineer for more details.