Variable Mu
Compressor
From Manley Labs:
The Manley Variable Mu® Limiter Compressor has defined professional stereo buss compression since 1994. This all-tube, transformer-coupled design utilizes the remote cut-off technique—re-biasing vacuum tubes to achieve gain reduction—delivering smooth, musical compression that unifies mix elements without audible artifacts. With custom hand-wound Manley transformers featuring nickel laminations and a fully differential signal path, the Variable Mu® provides exceptional transparency across its 20 Hz to 25 kHz frequency response.
The Variable Mu® offers two distinct operating modes for versatile dynamic control. Compress mode provides a gentle 1.5:1 ratio with soft-knee characteristics, ideal for adding cohesion and density to stereo busses. Limit mode delivers ratios from 4:1 to 20:1 with a sharper knee, providing precise peak control for recording and mastering applications. Both modes maintain the musical character and harmonic integrity that define the Variable Mu® sound.
Continuous refinement over three decades has enhanced the Variable Mu®'s capabilities, while preserving its fundamental character. Modern units incorporate a high-pass side chain filter, allowing the compression circuit to disregard low-frequency content and prevent bass-induced pumping. Offering hard-wire bypass, stepped input attenuators, and illuminated Sifam metering, the Variable Mu® delivers reliable performance with exceptional sonic clarity in the most demanding facilities around the globe.
Specs
- Transformers
- MANLEY input & output transformers with nickel laminations in mu-metal cases with flat frequency response from 20Hz-25KHz
- Inputs and outputs
- BALANCED INPUTS & OUTPUTS (600 Ohms)
- Circuitry
- Fully differential ALL-TUBE circuitry
- Variable gain vacuum tube
- 5670 x2 Standard or 6BA6 x4 T-BAR Mod
- Amplifying vacuum tubes
- 5751 or 12AX7 x2
- Output vacuum tubes
- 12BH7 x2 current production since 4/2016
- Side chain rectifier diodes
- 12AL5 x2
- Power supplies
- Independently regulated B+ and Heater supplies
- Bypass
- Hardwire BYPASS switch
- Input attenuator
- Stepped switch INPUT attenuator as of 10/2011
- Recovery, 5 steps
- 0.2s, 0.4s, 0.6s, 4sec., 8sec.
- Attack
- Variable ATTACK: 25msec-70msec
- Threshold
- Continuously variable THRESHOLD
- Ratio
- LIMIT (4:1 to 20:1) or COMPRESS (1.5 to 1)
- HP SC
- High Pass Side Chain Filter -3dB @ 100Hz
- Stereo link
- STEREO LINK SWITCH - Several units can be linked for Surround (custom order )
- Maximum gain
- 35dB
- Max. output
- +30dBu (26Vrms) 26dB Headroom
- THD
- <0.1% THD @ 1KHz
- Noise floor
- -85dB typical
- Power consumption (120/240VAC)
- 80 watts
- Mains voltage
- Unit is factory set for 100V, 120V or 220-240VAC operation for original destination country's mains voltage; Operating Mains Voltage changeable with power transformer changeover switch and fuse value change.
- Mains fuse value for 100~120VAC operation
- replace with 1.25A as of 10/2011
- Mains fuse value for 220~240VAC operation
- replace with 0.6A (600mA) as of 10/2011
- Mains fuse type
- MDA or MDL SLO-BLO Time delay 1 1/4" x 1/4"
- Mains voltage frequency
- 50~60Hz
- Dimensions
- 19” x 3 1/2” x 10” (chassis occupies 2u) Power transformer protrudes 3.5" out the back of the chassis.
- Shipping weight
- 23 lbs.
Source: Manley Variable Mu product page