Set it and forget it! Our Langevin ELOP® Limiter makes your job easy. The principle of operation is based around using a rectified sample of the audio to shine an LED (Light Emitting Diode) onto an LDR (Light Dependent Resistor). The photo-resistor in combination with a fixed resistor simply act as a changing voltage divider to attenuate the signal-- like a smart volume control. A similar principle was found in the older Teletronix & Urei LA-2A, LA-3, and LA-4 units which used a slower electro-luminescent panel-light on a conventional LDR encased in a light-tight enclosure. Ours uses modern VACTROL technology (but with a trick!) for exact sample-to-sample tracking and no high frequency loss while digging deep into limiting-- problems commonly associated with older LA-series limiters and other opto-based units. 

The audio signal passes only through all-discrete Class A amplifiers in the Langevin version. Each channel can be run separately or switched to "stereo - link". Due to their inherently quick attack, these Electro-Optical Limiters are skilled soldiers for tracking vocals or individual instruments. 

NOTE: In the summer of 2000 we ditched the superfluous "balance control".




  • ALL-DISCRETE audio path
  • Balanced XLR inputs & outputs and...
  • Unbalanced 1/4" inputs & outputs
  • Silent conductive plastic INPUT attenuators
  • ATTACK time 10mS for 6dB GR
  • RELEASE: 2.5 Seconds for 6dB GR
  • BYPASS switches
  • Sifam VU METERS
  • Meters switch to read OUTPUT or REDUCTION
  • STEREO LINK switch
  • <0.015% THD @1kHz
  • S/N Ratio: 126dB
  • Gain: -2 dB to 12 dB (adjustable)
  • Power consumption (120/240VAC): 24 watts
  • 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 1 3/4" x 10" (occupies 1u)
  • Shipping weight: 9 lbs.

Specifications subject to change because they just might.



Langevin Dual ELOP® Limiter 1994 - 2011,  Serial numbers LOP022 and up

Note: There were about 20 units built in 1993-1994 that used a different discrete line amplifier. These units had GREEN printed circuit boards and had UNbalanced in's and outs. Serial codes for those oldies are LOPTO001 through LOPTO021. Scroll down for calibration details for THOSE units.



We frequently get asked a number of questions regarding Langevin, including the proper pronunciation of the name. (the 'g' is soft like in 'gelatin' or 'orange').

Langevin was one of the original pro audio manufacturers dating back to WWII. In that era there were far fewer audio manufacturers and Langevin gear was very popular and especially respected in the broadcast industry. There were very few recording studios then and most of them relied on Langevin, Altec, Fairchild, and other great brands as well as home-made gear. Early Langevin equipment was vacuum tube based and later became mostly discrete transistor based. Today, you can often find vintage Langevin pieces still in use after all this time.

Are these the exact same circuits as the vintage pieces?

The mic preamplifier and EQ borrow some ideas from the old circuits but are not identical at all. We designed new gain blocks to deal with the balanced/unbalanced saga better than they used to in the olden days. And of course, we use new parts! Transistors, pots and most components have become significantly improved over the last 30 years. The limiter is a blend of the old discrete style of Langevin discrete and the also vintage 'LA' series of Levelling Amplifiers. Manley developed a similar opto-based limiter and has used it in the Manley ELOP® Limiter, Langevin ELOP® Limiter, Langevin Dual Vocal Combo, and the VOXBOX® limiter / de-esser section.

What's the difference between a Manley Pultec or ELOP® Limiter and a Langevin one?

The Manley units are all-tube while the Langevin units have all-discrete make up gain amplifiers. The EQ or limiting and metering sections are all the same Manley-to-Langevin. Your choice becomes between the sound of discrete transistor cicuitry in the Langevin gear or vacuum tubes with and without transformers in the Manley gear. Different flavours, but all build side-by-side with all high quality parts and reliable construction techniques at the Manley Labs factory. Take an on-line factory tour here!

Do we support any of the vintage Langevin products?

Sorry, no. We just bought the name and rights to use any of the old circuits. We didn't build the old stuff and never have had parts or real documentation. The usual experts on vintage gear and restoration are your best bet.




PURPOSE: To calibrate the ancient first version ELOPs that we haven't built since 1994. 
METHOD: To relate the old board layout to the current Owner's Manual.
UNITS AFFECTED: Serial numbers for units that will benefit from this update are LOPTO001 (7/1993) through LOPTO021 (2/1994).




Trimmer "1" adjusts the Power Rail Voltage

Trimmer "2&3" is the Preamp GAIN adjust

Trimmer "6&7" is the Meter Zero Cal

Trimmer "8&9" is the Gain Reduction meter Cal

The other trimpot adjusters referred to in the manual do not exist in this version of Langevin ELOP.

For further info, please contact our Service Department. If you would like to send your unit in and have Paul perform this calibration for you, please contact him by filling in the service form on that page.