Manley Stereo Variable Mu Mastering Version “The Works”

$7,899.00

Stereo Variable Mu® Limiter Compressor THE MASTERING VERSION “The Works”

Proudly from our beginning, we at MANLEY LABS have been closely involved with numerous mastering facilities around the world. For these most demanding engineers in our industry, we have created specialized products such as our all-tube tape repro head amps, digital converters, high-powered vacuum tube monitor amplifiers, through to custom monitoring consoles, all the way up to complete facility design and installation.

The Mastering Version

The Mastering Version of our Variable Mu® Limiter Compressor incorporating detented and logable steps built with 1% metal film resistors on sealed gold-contact Grayhill switches is available. NO, we will not mod a “normal” unit to the Mastering Version. The Mastering Version of the Variable Mu Limiter Compressor uses expensive Greyhill rotary switches with gold contacts where conductive plastic pots were used. The steps are determined with a large number of 1% precision metal film 1/2 watt resistors. The best conductive plastic pots only have 10% or 20% tolerance. The ten fold improvement in precision helps a great deal in left-right matching. There is a subtle audible improvement with stepped switches as well. Audiophile HI-FI often uses that technique to wring the last drop of performance out of a preamplifier. And I bet you wanted stepped switches mostly for resets.

The INPUT LEVEL is a five position switch with a generic optimum setting of “0” in the 12:00 position. Each step in either direction is 2 dB. For reference, Unity Gain is “0”.

The OUTPUT Attenuators are in half dB steps. Reference Unity is -11.5 or fully counter-clockwise. You might think of these as “gain makeup”. They are marked technically, in that “0” or fully clockwise has zero attenuation in the circuit. The tube circuit actually has 15.5 dB of gain. The Input attenuator at “0” removes 4 dB and the Output attenuator removes the last 11.5 producing “unity”. With a little compression the “gain make-up” available with the Output Attenuator is very handy.

The Threshold is in half dB steps calibrated to LIMIT mode. In Compress the steps are approximately 1/4 dB. There are 24 steps so LIMIT gets a 12 dB range and Compress has a 6 dB range of adjustment. In some cases it is common to use the Input Attenuator to find a good starting point. Some Mastering engineers find using the combination of Input, Output and Threshold to achieve a little different “drive”. Another good reason for stepped gains.

The Attack Time has been slightly extended in both directions compared to a regular Variable Mu and divided into 11 steps.

The Recovery 5 position switch is exactly the same as a regular Variable Mu.

The Switches

  • 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 LIMIT (24 detents) and 24 x 1/4 dB steps in COMPRESS
  • Attack: 11 positions CW (fast) 15mS, 20, 25, 30, 35, 40, 50, 60, 70, 80, 90mS (slow) CCW
  • Release: 5 positions CW (fast) 200mS, 400mS, 600mS, 4S, 8 Seconds (slow) CCW

T-Bar Mod

Backstory: The newer Variable Mu units use 5670 tubes instead of the 6386. By now the availability of the original USA GE 6386 is poor; we don’t have any left at all, and what we do have are not usable due to noise, microphonics, bad side-to-side match, etc.

So does the 5670 sound different? Well, up to about 6db of limiting it’s about the same. After that point, the 5670 version tends to sound more “squashed” than the original 6386 version. Some like it better, some don’t – depends on what you’re trying to do.

To solve all these problems, Paul came up with a really good solution: the T-Bar Mod. This uses a pair of 6BA6 pentodes wired as single triodes to replace each dual triode 5670 (or 6386). The 6BA6 T-Bar Mod is the preferred system to use in the Manley Variable Mu® for reasons of ability to perfectly match each phase-halve section and each stereo set, ability to select for lo-noise and lo-microphonic sets for a low cost, and because the action of the 6BA6’s so closely resemble the smooth 6386 limiting curves.

We can add the T-bar mod to your Variable Mu unit – contact our Service team for more information, and read more about Paul’s special T-bar mod here.

You won’t see any differences on the front panel aside from different meter scaling, whose left-most number is 12dB of reduction instead of 10dB.

Also of note – both the Manley NU MU’s LIMIT and COMPRESS reduction curves are very, very similar to those in a T-BAR modded Stereo Variable Mu. Check them out in this graphic.

MID/SIDE (a.k.a. Vertical/Lateral, or Sum/Difference)

This modification 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. Read more about the MS Mod in the Owner’s Manual.

In order to add both M-S and the HP SC mods, we move the power switch to the rear panel and install both channels’ HP SC switch to the center hole where the power switch was. The M-S switches then flank this switch.

  • 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 LIMIT(24 detents) and 24 x 1/4 dB steps in COMPRESS
  • Attack: 11 positions CW (fast) 15mS, 20, 25, 30, 35, 40, 50, 60, 70, 80, 90mS (slow) CCW
  • Release: 5 positions CW (fast) 200mS, 400mS, 600mS, 4S, 8 Seconds (slow) CCW
  • Input Tubes: 2 x 12AT7A NOS GE specially selected by Manley Labs for lo-noise and stable bias
  • Output Tubes: 2 x 12BH7 (or 6414W NOS USA) dual triodes
  • Balanced XLR Line I/O: MANLEY IRON® transformer-coupled Balanced Inputs and Outputs
  • Gain: 20dB max Limiter Gain
  • Input Impedance balanced input XLR combo jack: 2 kOhms
  • Input Impedance unbalanced input 1/4” combo jack: 10 kOhms
  • FET Limiter: Attack: approx. 100μS; Release: 10mS to 2Sec; Ratio: better than 20:1
  • ELOP Limiter: Attack: approx. 10mS for 6dB GR; Release: 2.5 Sec; Ratio: 10:1
  • Frequency Response: 5Hz to 60KHz
  • Maximum Output: +32dBm, +30dBm (into 1KΩ load)
  • THD+N: <.05% @ 1KHz
  • Dynamic Range: 115dB typical
  • Output Impedance: 200Ω
  • Power Consumption Slam! Analog: 0.480 Amps (480 milliamps = 480mA) @ 120V = 57.6 Watts
  • 0.240 Amps (240 milliamps = 240mA) @ 240V = 57.6 Watts
  • Outboard Power Supply: factory set for 100V, 120V or 220-240VAC operation for original destination country’s mains voltage.
  • Operating Mains Voltage: changeable with power transformer re-wiring via switch and fuse value change.
  • Mains Voltage Frequency: 50~ 60Hz
  • Size: 19” X 12” X 3.5” (occupies 2u)
  • Shipping Weight: 25 lbs.