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Manley Labs Variable Mu Mastering Version

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MMSSLCHP - Manley Variable Mu Mastering - Stereo Tube Limiter Compressor - Mastering Version

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 Manley Variable Mu Mastering Version uses detented switches instead of pots and let you easily dial up or log favorite settings.

*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.

*The T-Bar option brings back the sound of the 6386 tube used in the early versions of the Variable Mu and the Frairchild 670. It makes the Variable Mu even smoother when pushed past 6dB of compression. Using two matched 6BA6 pentodes strapped as triodes makes this choice better than an unobtainable & unsortable 6386.


- Stereo Fairchild 670-type Limiter Compressor
- Fully differential ALL-TUBE circuitry using 5670, 5751 (or 12AX7), 7044 (or 5687), & 12AL5 per channel
- MANLEY input & output transformers with nickel laminations in mu-metal cases with flat frequency response from 20Hz-25KHz
- Stepped switch Dual-input attenuator
- Stereo and dual-mono mode
- Soft-knee Compression (1.5:1) or limiting (4:1 to 20:1)
- 100 Hz High Pass Side Chain Filter (selectable)
- Hard-wire bypass
- Large Sifam VU meter gain reduction
- Mastering Version featuring fully detented logable steps for accurate recall of settings

Technical Specifications

- Detented controls: Input: -4 to +4 in 2 dB steps, Output: -11 to 0 in 1/2 dB steps (24 detents), Threshold: -11 to +1 in 1/2 dB steps (24 detents), Attack: 11 positions, Recovery: 5 positions
- Input/output transformers: MANLEY nickel laminations transformes in mu-metal cases
- Frequency response: 20Hz-25KHz
- Input impdance: 600 ohms
- Output impdance: 600 ohms
- Tubes: 5670, 5751 (or 12AX7), 7044 (or 5687), & 12AL5 per channel
- Recorvery time: 5 steps: 0.2sec, 0.4sec 0.6sec, 4sec, 8sec
- Attack time: 25msec - 70msec
- Ratio: LIMIT (4:1 to 20:1) or COMPRESS (1.5:1)
- High Pass Side Chain Filter: -3dB @ 100Hz
- VU meter: Large illuminated Sifam VU meters for output or gain reduction
- Maximum gain: 35dB
- Noise floor (<0.1% THD @ 1KHz): -85dB typical
- Mains Voltage: 100V, 120V or 220-240VAC / 50~60Hz (with different transformers)
- Power Consumption (120/240VAC): 80 watts
- Dimensions (W x H x D): 483 x 89 x 343 mm (19” / 2U)
- Weight: 6.4 kg