Manley NU-MU
terCompressor With Stereo Optical, Tube, Hybrid


The Variable Mu Limiter Compressor is the glue that holds the mix together while crystallizing it into a professional, final product. High Pass Side Chain mod now comes standard.

It works by using the "remote cut-off" or re-biasing of a vacuum tube to achieve compression. Even the side-chain has glowing rectifier bottles. The unique 5670 dual triode is at the center of the peak-reducing and compression action constantly being re-biased by the vacuum tube rectified side-chain control voltages which cause this tube to smoothly change its gain.

The COMPRESS mode is soft-knee 1.5 to 1 ratio while the sharper knee LIMIT mode starts at 4 to 1 and moves to a more dramatic ratio of 20 to 1 when limiting over 12 dB. Interestingly, the knee actually softens as more limiting is used. Distortion can be creatively used by turning up the Input and turning down the Output while using very little or no compression.

The High Pass Side Chain mod comes stock on all Manley Variable Mu limiter/compressors since 12/2009, on both regular and mastering versions. This mod adds two switches to the front panel, one for each channel, so that when engaged, the side chain will not respond to frequencies lower than 100 Hz. This HP SC Mod can be used with music with heavy bass lines or bass-heavy mixes where you don't want the bass driving the whole action of the compressor.

The filter is a very gentle 6 db per octave 1 pole filter, and will typically be down 1-3 db at 100 Hz, and down 4-6 db at 50 Hz. As you decrease the frequency the amount of limiting will decrease also. At the extreme LF (less than 20 Hz) there should be very little gain reduction going on.

Manley Laboratories NU-MU Specifications:

  • Input & output transformers with nickellaminations in mu-metal cases with flat frequency response from 20 Hz-25 kHz
  • Balanced inputs and outputs (600 Ohms)
  • Fully differential all-tube circuitry using one each5670, 5751 (or 12AX7), 7044 (or 5687), & 12AL5 per channel
  • Independently regulated B+ and Heater supplies
  • Hard-wire bypass switch
  • Stepped switch iNPUT attenuator as of 10/2011 (older units use Silent dual-ganged potentiometer)
  • Recovery 5 steps: 0.2 s, 0.4 s, 0.6 s, 4 sec., 8 sec.
  • Variable attack: 25 msec-70 msec
  • Continuously variable threshold
  • Limit (4:1 to 20:1) or compress (1.5 to 1)
  • HP SC: High Pass Side Chain Filter -3 dB @ 100 Hz
  • Large illuminated Sifam meters (older units before serial number MSLC61642 shipped before 12/2003 use: 26 V 1.2 W FESTOON
  • LAMPS; Manley's Part Number: VAR016 B) Order spare bulbs using our parts order form. (newest units after serial number)
  • MSLC61642 shipped after 12/2003 use white LED lighting)
  • Stereo link switch
  • Several units can be linked for Surround (custom order )
  • Maximum gain: 35 dB
  • Maximum output: +30 dBu (26 Vrms) 26 dB Headroom
  • <0.1% THD @ 1KHz Noise floor: -85 dB typical
  • Power Consumption (120/240VAC): 80 watts
  • Unit is factory set for 100 V, 120 V or 220-240 VAC operation for original destination country's mains voltage
  • Operating Mains Voltage changeable with power transformer change over 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 (600 mA) as of 10/2011
  • Mains Fuse Type: MDA or MDL SLO-BLO Time delay 1 1/4"x 1/4"
  • Mains Voltage Frequency: 50~60 Hz
  • 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
Add to Cart

We're sorry, only of this item available

Call a Sales Pro at for more information

Serving Contractors, Dealers, and Installers Since 1977

Contact: 1-800-828-0509 / Hours: Mon - Fri 7:00AM - 7:00PM