written by
Ziga Rezar

Dual LA-2A Tutorial

Gear Tips 3 min read

Yes, we finally did it! An LA-2A is available at mix:analog!

Video tutorial with sound samples

The LA-2A is a synonym for smooth, musical compression. Thanks to the combination of a naturally pleasing character of optical cells and simple controls, it deserves to be called a classic.

Its name says it all. The “Leveling Amplifier is most useful for this very task - transparently leveling out the volume of the track and amplifying the average volume. Subsequently, it’s probably no surprise that it is found on more than half of all the vocal tracks ever recorded! You should also try it on bass guitars, acoustic guitars, and other highly dynamic tracks. The LA-2A is a king of transparent volume riding.

Teletronix Vintage LA-2A opto compressor
The original LA-2A design

The Dual LA-2A that is available at mix:analog is not a vintage Teletronix unit. Instead, it is a meticulous recreation of the original circuit with vintage components wherever it made sense to retain the sonic character of the venerable compressor. For instance, the input and output transformers are original UTC units, and the “Slow” optical cell is an original vintage UREI T4B.

This gave us the freedom to implement the Feedback modification in the tube amplifier and fit a stereo unit and all the automation into one 3U enclosure.

LA-2A Controls

LA-2A GUI left side controls
The left side of the GUI


The Gain knob works as a make-up gain after the compression cell. For this reason, it doesn’t “push the level” into the compressor, but only affects the output volume, making the track louder.


This control is not on the original units, but many studios have added it to their units. The modification looked so promising when we came across the idea that we couldn’t resist implementing it.

What the Feedback knob does is change the response of the tube make-up gain stage, effectively giving you control over the amount of its harmonic distortion. Since this is negative feedback, more of it means less gain and less distortion, and less of it means more gain and more distortion.

This modification is not meant to turn the LA-2A into a distortion box, although you can push it and it will become noticeable when pushed really loud. The range of the Feedback knob in combination with the Gain control allows for gentle thickening of the low-mid part of the spectrum as you would expect from driving a tube summing mixer or console.


This is a true relay bypass.

Linked/Dual Mono

This switch controls both the graphical interface and the internal sidechain link for stereo or dual-mono operation. In dual-mono mode, the controls and sidechains of both units are completely independent.

GR/VU +4

This switch toggles the meter source between gain reduction and output level. Note that the VU reading is according to a fairly conservative (approximately) 0dBu, which means the unit can take quite a bit more level than a 0VU reading. Still, when driven hard to “pegging meter” levels, the distortion is going to get noticeable.

LA-2A GUI right side controls
GUI - Right side

Peak Reduction

This is the “compression knob”. Turn it clockwise for more compression, and that’s it! No twiddling around with timing constants and ratios and so on, this is as simple as it gets.


We promoted the famous, yet inconspicuous little adjustment screw named “R37” on the LA-2A schematic to a full-fledged control knob. This is an adjustable sidechain filter that attenuates the low frequencies for up to 10dB, effectively providing a high-emphasis for the frequencies above 1kHz.

Use it to avoid pumping on kick and snare hits when processing stems or whole mixes and to avoid excessive sibilance when compressing vocal tracks.


The Fast/Slow switch changes the optical cell used for compression. A different cell will offer different attack and release constants and ratio curves, so experiment a bit and find which one fits your source material best.

The SLOW cell is an original vintage UREI T4B. Not a clone, not a remake, this is the exact cell that was found in the vintage LA-2A units.

The FAST cell is a modern take on the electroluminescence panel/photo-resistor combo made by DRIP electronics, an audiophile-grade DIY recording gear provider.


This setting originally came as a “mod” by Teletronix themselves! The Limit mode changes the ratio from approx. 3:1 to something closer to 10:1, but the exact curves of both modes are not available in the original manual.

Sound samples


LA-2A GUI at mix:analog
LA-2A user interface at mix:analog

The Dual LA-2A is available at mix:analog right now! It will be completely FREE of charge for 30 minutes of use each day during the promotion period! Simply make a reservation and try it out on your own material!

compressor la2a tutorial