The Manley Labs Stereo MU Limiter Compressorfrom Manley Labs Stereo MU Limiter Compressoris a dynamic signal processor using two single-pentode tubes wired in triode for peak reduction and compression. The tube circuit is constantly re-biased by the vacuum tube rectified side-chain control voltages, resulting in a smooth change in gain.

The Mid/Side modification (also known as the Vertical/Lateral or Sum/Difference) allows for stereo encoding and decoding, as well as image enhancement processing capabilities. Instead of an active circuit, the left switch changes the wiring of the input transformer, while the right switch changes the output wiring. When both M/S switches are activated, the stereo signal is encoded and decoded providing the ability to compress the mid, sum or mono part of the sound on channel one, while channel two's compressor controls the side or difference. The Mid/Side switches replace the high-pass side-chain position on the front panel. The HP/SC are ganged and moved to the power switch position, while the power switch has been moved to the rear of the chassis.

The T-Bar modification uses a converter board with two 6BA6 single pentodes wired in triode mode to take over the duties of the single-envelope dual-triode 6386 or 5670 tubes. Each of the single-pentode tubes are matched for low noise and low microphonics before being installed onto the adapter board. Direct A/B comparisons and testing have found the sound and performance of the dual 6BA6 to be nearly identical to the original 6386 tube. Comparing the dual 6BA6 to the 5670 sounds less "squashed" with fewer artifacts as the amount of limiting is increased.

The compressor setting offers a soft-knee 1.5:1 ratio, while the limit mode offers a sharper knee with ratios ranging from 4:1 to 20:1. With higher limiting settings, the knee will start to soften. Distortion effects can be achieved by turning up the input and lowering the output while using little or no compression. The side-chain high-pass filter uses a 1-pole, 6 dB/octave filter that attenuates 1 to 3 dB at 100 Hz and 4 to 6 dB at 50 Hz. Once engaged, the compressor / limiter will not respond as strongly to low frequency content and will prevent audible "pumping" when processing bass-heavy music.

The input of the Variable MU is ganged, but can still process two independent channels with separate threshold and output controls. With the link switch engaged, the unit operates in true stereo mode and excels at processing 2-track, final mix, or mastering compression and limiting. Handmade in the USA, the unit is housed in a 2U steel chassis with a CNC-machined 1/4" faceplate that is also inlaid with laser-engraved inserts. The Variable MU ships with an IEC power cable.

Sound of the Original Variable MU    Mid/Side Mod Adds Stereo Enhancement    All-Tube Design    6 x Tubes per Channel    Hand-Wound Custom Nickel Transformers    Stereo or Dual Mono    Hardwire Bypass Switch    Side-Chain High-Pass Filter    Large Illuminated Sifam Meters    Handmade in the USA

• M/S modification allows various approaches to Mid/Side recording, playback and processing
• T-Bar Mod replaces the single 5670 tube with two 6BA6 tubes providing the original sound of the Variable MU
• Manley input and output transformers with nickel laminations in mu-metal cases
• Balanced inputs and outputs (600 Ω)
• Independently regulated B+ and heater supplies
• Bypass Switch: Hardwire true bypass
• Input Attenuator: -8 to +8 dB stepped Greyhill switch
• Variable Attack: 25 to 70 ms
• Threshold: Continuously variable
• 5-Step Recovery Switch: 0.2, 0.4, 0.6, 4, 8 sec
• Compression Ratio: 1.5:1
• Limit Ratio: 4:1 to 20:1
• Large Illuminated Sifam Meters: Displays the amount of dB gain reduction
• Stereo link switch

Related Questions and Answers

Q: 1. would an audio gate alone control help in a 4mic clip on mic situation that is very interactive?

A: First of all the gate function is designed to keep the signal muted until a level you choose to open the channel. This would not help the clip at all. If, on the other hand if you were to use the compressor side of the dbx you may be able to adjust the input and output to eliminate the clipping altogether. I would suggest adjusting the output of each channel so each channel will not exceed the headroom on the mixer, then send the combined signal into the dbx and use the compressor to clamp down on the signal a bit. There is training available for this. I am using my 266xs to make a talk show with four funny ladies, who laugh a lot and loudly fit into the available headroom while recording for broadcast. without the compressor the laughing just clips so badly the recordings are not able to be used.

Q: 2. Can this device help me, to have the same volume always from my tv to the speakers.?

A: The DBX unit is a dual channel unit generally recommended for professional music recording/production. The unit also features a Gate and Expander. Most features not required for your application. The Rolls SL33B is a popular product for your application, and can be connected between TV and receiver, or TV and powered speakers. https://bhpho.to/2qGDGNG

Q: 3. Is this compatible with Protools 10?

A: The IK Multimedia T-RackS 5 Dyna-Mu Compressor Software will run in digital audio workstations that support 64-bit AAX, AU, VST2, VST3 plugins. Natively, Pro Tools 10 supports only 32-bit plugins so T-TrackS 5 is not compatible with Pro Tools 10 but is compatible with Pro Tools 11.

Q: 4. Is the headphone amplifier RF protected? Time ago I bought a ROLLS PM-55 and I had problems with cellular phones interferences

A: No RF issues, but I did have grounding issues with one I bought recently.

Q: 5. The recommended accessories for this microscope include batteries. Could you please advise why batteries are necessary? I assume that they are required for field work where there is no power supply, but this is not mentioned in the specification.

A: This model does not take batteries. My apologies for the confusion. I will contact the Web Team to take this accessory down.

Q: 6. Would this be a good device for evening out the crazy volume levels on my tv?

A: Absolutely! Very simple...just set the Makeup Gain control at the 0 position, and set the Threshold to a level that brings down the extremely loud audio to a level near that of a normal listening level. If you hear the limiter pumping or breathing too much on louder program audio, lower the input level and tweak the Makeup Gain a bit to even things out. It works great for my hard-drive based music collection, which varies greatly in level due to the variety of formats and recording techniques used over the past 4 decades!

Q: 7. Can this device be made to stay in Super Nice mode across power cycles?

A: Settings will not be remembered in the case of a power failure or a power reset. NORMAL MODE: Mode Selection This mode is selected upon power up of the RNC. If the SUPER NICE indicator lamp is extinguished, then NORMAL MODE is selected. SUPER N ICE MODE Mode Selection: This mode must be manually selected by depressing the SUPER NICE switch until the SUPER NICE indicator lamp is on.

Q: 8. Can the Rolls PM55P pass through Phantom power?

A: The Rolls PM55P Stereo Personal Monitor Amplifier with Optical Limiter (BH # ROPM55P) will pass PHANTOM POWER with no voltage or signal loss.

Q: 9. Will this item work with a condenser boom mic (provide phantom power)?

A: I don't think it provides phantom power but it does allow it to pass through? So send phantom power from the recorder (or TX if going wireless) and you should be good.

Q: 10. So would I be able to use this to limit the volume on my home receiver, so that once the speakers reach a certain volume they won't get any louder past the set point?

A: I use it for headphones in a live band setup but it will work for a home stereo. If you want to limit an single source say a TV just connect inline. To limit multiple sources use a preamp in/out or tape in/out.