THE STUDIO STANDARD IN TUBE COMPRESSION
Stereo Compressor/Limiter , All Tube Design
The MANLEY VARIABLE MU® LIMITER COMPRESSOR is one of the very few compressors that has become a real standard in Mastering studios and contributed to most hit records over the last decade and probably the next. "Mu" is tube-speak for gain, and Variable Mu® is our registered trademark for this limiter compressor. It works by using the "remote cut-off" or re-biasing of a vacuum tube to achieve compression. The precious vintage Fairchild 670 also uses this technique and is one of few all-tube compressor to do so, that we know of. Even the side-chain has glowing rectifier bottles. How’s it work? 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. Just like that.
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 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 Output while using very little or no compression.
You might notice that the Variable Mu® Limiter Compressor has a ganged input control, but do not jump to conclusions that it is mono-unfriendly. Track away! There are separate threshold and output controls to make compensations with plus you can always adjust your individual source levels elsewhere, right? The advantage of the stereo input control becomes dramatically clear when you switch to LINK mode, and that’s what our Variable Mu® Limiter Compressor does better than anything else: final mix, 2-track, or mastering limiting and compression. Like one reviewer put it: “It’s like pouring a bowl of sweet cream over the mix.” Mmmmmm. Yummy. Give your music a big hug.
The High Pass Side Chain option is now a STANDARD OPTION on all Mastering Versions or Normal Variable Mu limiters. This 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 100Hz. (We standardly use 100Hz as the -3dB point. Other frequencies can be custom ordered.) 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 6db per octave 1 pole filter, and will typically be down 1-3db at 100 Hz, and down 4-6db at 50Hz. As you decrease the frequency the amount of limiting will decrease also. At the extreme LF (<20hz) there should be very little gain reduction going on. The whole intent of the filter was to keep very LF stuff (like a heavy kick drum) from activating the compression/limiting so that the overall level didn't duck with every drumbeat.
Another mod we can do for several Variable Mu's is to accommodate Surround Sound Linking. This presumes you want to use 4 to 6 (or more) channels of Variable Mu for your 5.1 surround work, and you own two or three Stereo Variable Mu units (or more). For this we add a pair of RCA jacks on the back of each unit so that the sidechain can be easily plugged into another one or two other Stereo Variable Mu units. Then the LINK switch is replaced with a three-way switch and wired to select amongst the following three conditions:
LINK: Link the side-chains of the two channels in this chassis
EXT: Link the side-chains of the two channels in this chassis AND to the other units plugged into the RCA linking sidechain access jacks on the back of the unit.
SEP: Do not link to any other channels
We add TWO RCA jacks to each unit for easy daisy-chaining. Just use any ol' RCA cables you have lying around to link up the sidechains. Then all the sidechains track each other. You still have to set up each unit as you would though, as the very act of linking the side chains does not create a master-slave situation.
Features and Specifications:
- MANLEY input & output transformers with nickel laminations in mu-metal cases
- FREQUENCY RESPONSE -1dB: 20Hz-75KHz screenshot
- BALANCED INPUTS & OUTPUTS (600 ohms)
- Fully differential ALL-TUBE circuitry using one each 5670, 5751, 7044 or 5687, & 12AL5 per channel
- Independently regulated B+ and Heater supplies
- Hard-wire BYPASS switch
- Silent conductive plastic dual INPUT attenuator
- 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)
- 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 Voltage Frequency: 50~ 60Hz
- Dimensions: 19” x 3 1/2” x 10” (chassis occupies 2RU) Power transformer protrudes 3.5" out the back of the chassis.
- Shipping Weight: 23 lbs.
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Manley Variable MU Manual (62,03 KB)