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ManleyVariable Mu Limiter Compressor - MS Mod + T-Bar Mod


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Manley Variable Mu

Combining their two fantastic modifications into one unit, the Variable Mu MS mod & T-Bar mod from Manley is a stereo limiter and compressor that offers tons of functionality, unbelievable dynamic control, and a huge sound. Known as "The Works", this edition of the Variable Mu ties together the fantastic mid/side encoding and decoding alongside the tube replacements that lean more towards the original tubes from yester-years' Variable Mu. However, the glimmer and glam are not just fancy bells and whistles, but useful tools to add depth and control over the fantastic dynamic processing the Variable Mu is known for on mixes, two-tracks, and masters.

Each step of the way, the Variable Mu takes tube gain staging (hence the Mu), amplification, and leveling with maximum high-voltage headroom for a clean and powerful signal. The input gain is ganged for both channels, but this should be seen more as a pro than a con considering it's general use for stereo mixes and two-tracks. Each channel can be set to a gentle compressor with a 1.5:1 ratio, or be pushed into maximum drive with a limiter that starts off at a 4:1 ratio but pushes up to 20:1 once the gain reduction surpasses 12dB.

Dynamic control is implemented with a continuous threshold control for fine-tuning gain reduction, while the time shaping tools feature a relatively smooth attack time of 25ms to 70ms and a quite slow release with times of 200ms all the way to 8 seconds. All three of the controls can be set individually or in a stereo link for one set of controls affecting both channels, and all compression and limiting can be easily viewed via the backlit gain reduction VU meters. The final output controls are unique for each channel making it very easy to dial in the perfect amount of leveling per channel.

Looking specifically at the modifications, the MS mod provides selectable input and output mid/side encoding and decoding, offering a large assortment of stereo options such as squashing the mids while keeping the sides lively or even utilizing in a broadcast scenario where heavy usage of mixing mid/side is important. The T-Bar mod on the other hand is more of a flavor change back to the stylings of the less obtainable 6386 tubes by putting in a pair of 6AB6 pentodes that are rewired as single triodes. This change not only replicates the reduction and limiting curves found in the 6386 tubes, but also takes out the poor quality found in current ones that push noise and microphonics.

The Variable Mu "The Works" edition from Manley is the end-all-be-all for those looking for maximizing their usage and versatility out of a classic bus compressor/limiter—that still persists to this day for its epic sound.

Variable Mu Features

  • Stereo tube limiter/compressor
  • Mid/side encoding and decoding via input/output switching
  • T-Bar mod replaces dual triode 5670 with a pair of 6BA6 pentodes wired as single triodes
  • Balanced transformer inputs and outputs with flat frequency response
  • All-tube signal path, including variable gain, amplifying, and output
  • Each channel has a limit/compress switch and a hardware bypass switch
  • Compression is soft knee at a 1.5:1 ratio, Limiter is a sharper knee starting at a 4:1 ratio and can achieve up to a 20:1 ratio
  • Detented input gain ranging +/-8dB over an 11-position control
  • Continuous control over threshold and attack (25 to 70ms)
  • 5-position recovery control (200ms to 8 sec)
  • HP SC input sets a 1-pole filter at 100Hz
  • Sep/Link sets whether the threshold, attack, and recovery are individual to the channels or linked controls
  • 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
  • Output vacuum tubes: prior to MSLC94006 use 7044 or 5687 x2
  • Side Chain Rectifier Diodes: 12AL5 x2
  • Independently regulated B+ and Heater supplies
  • Hardwire BYPASS switch
  • Stepped switch INPUT attenuator as of 10/2011. (older units use Silent dual-ganged potentiometer)
  • RECOVERY 5 steps: 0.2s, 0.4s, 0.6s, 4sec., 8sec.
  • Variable ATTACK: 25msec-70msec
  • Continuously variable THRESHOLD
  • LIMIT (4:1 to 20:1) or COMPRESS (1.5 to 1)
  • HP SC: High Pass Side Chain Filter -3dB @ 100Hz
  • Large ILLUMINATED Sifam METERS (older units before serial number MSLC61642 shipped before 12/2003 use: 26V 1.2W FESTOON LAMPS
  • Manley's Part Number: VAR016B) 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: 35dB
  • Max. output: +30dBu (26Vrms) 26dB Headroom
  • <0.1% THD @ 1KHz Noise floor: -85dB typical
  • Power Consumption (120/240VAC): 80 watts
  • 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.
Manley Variable Mu Limiter Compressor - MS Mod + T-Bar Mod Reviews