Manley Labs Stereo Variable MU Limiter Compressor

The Variable Mu Limiter Compressor is the GLUE that holds the mix together while crystallizing it into a professional, final product. All-tube, all transformer, an all-American legend. High Pass Side Chain mod now comes standard.• Manley input & output transformers with nickel laminations in mu-metal cases with flat frequency response from 20Hz-25KHz • Fully differential ALL-TUBE circuitry using one each 5670, 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) • 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 their 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 ) • 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.The MANLEY VARIABLE MU LIMITER COMPRESSOR has been their best selling product for many years. It 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 Manley's 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. See the gain reduction curves here!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 Manley 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 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 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 (less than 20Hz) there should be very little gain reduction going on. The whole intent of the filter is to keep very LF stuff (like a heavy kick drum) from activating the compression/limiting so that the overall level doesn't duck with every drumbeat.Another mod they 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 they 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 channelsWe 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.