The Teletronix LA-2A Compressor

At first glance, the Teletronix LA-2A looks simple, but behind its plain panel is a design that shaped the way compression was approached for decades.

History of the Teletronix LA-2A

The LA-2A Leveling Amplifier was introduced in the early 1960s by James F. Lawrence II, founder of Teletronix in Pasadena, California. Lawrence was looking for an alternative to the variable-mu tube compressors that were common in broadcast and studio work. His approach was to use an electro-optical attenuator, creating gain reduction through light and a photocell instead of complex tube circuitry. This idea drew from earlier designs like the Gates Sta-Level, but the LA-2A introduced a simpler, more streamlined optical system built around the T4 electro-optical cell.

Development and Early Models

Before the LA-2A, Teletronix released the LA-1A and LA-2. These early units showed promise but had technical limitations that made them less practical for regular use. The LA-2A improved the design by introducing the T4 cell, which contained both a luminescent panel and a photoresistor in one module. This allowed the circuit to respond naturally to signal changes, creating smoother attack and release characteristics without complex controls.

Design Changes and Versions

The first production LA-2As, often called “grayface” units, were built from about 1962 to 1965. In 1965, Teletronix introduced the “silverface” version, which continued until around 1969. Component variations between runs led to small differences in behavior, but the overall design remained consistent.

Ownership Changes

In 1967, Teletronix was sold to Babcock Electronics, which later transferred rights to Studio Electronics. Eventually, Bill Putnam Sr.’s Universal Audio acquired the design, ensuring continued availability. Although original production ended in the late 1960s, Universal Audio reintroduced the LA-2A decades later, carefully following the original schematics and T4 cell construction.

Timeline of Key Versions

• Early 1960s – LA-1A and LA-2 developed as first optical compressor prototypes
• 1962 – LA-2A “grayface” version released
• 1965 – LA-2A “silverface” version introduced
• 1967 – Teletronix sold to Babcock Electronics
• Late 1960s – Rights pass to Studio Electronics, then Universal Audio
• 1969 – End of original LA-2A production
• 1990s onward – Universal Audio reissues LA-2A with original-style T4 cells

Software Emulations

• Universal Audio Teletronix LA-2A Collection
• Waves CLA-2A
• Native Instruments VC 2A
• IK Multimedia T-RackS White 2A
• Plugin Alliance NEOLD U2A

Tips and Techniques

• Learn the difference between Compress and Limit modes

  Most LA-2A plugins have a switch between Compress and Limit. In Compress mode, the ratio sits around 3:1 to 4:1 and adjusts naturally depending on the source. Limit mode pushes the ratio higher, creating a harder knee. To try this: insert the plugin on a vocal track, set Peak Reduction for about 4–6 dB of gain reduction, then flip between modes. Compress will sound slightly smoother; Limit holds the level more firmly, ideal for bass or drums. The difference is subtle.

• Understand attack and release behavior

  The LA-2A reacts automatically, without knobs for attack or release. Attack averages around 10 ms but varies with frequency content. Release is “program-dependent,” changing based on how long and how hard the signal stays above threshold. Put the plugin on a vocal and listen as it releases gently at the end of phrases. On drums, the release may feel slower, smoothing transients. For more punch, try parallel compression.

• Compare different plugin emulations

  Each developer models the LA-2A slightly differently. UAD’s version includes multiple models (Silver, Gray, and Legacy), while Waves’ CLA-2A is modeled after a specific hardware unit with a brighter character. IK Multimedia’s White 2A is different as well. Load two versions on separate tracks and A/B them to hear which fits best. For example, use UAD on vocals and Waves CLA-2A on guitars for varied tonal character.

• Use the Gain control properly

  The Gain knob on LA-2A plugins is makeup gain applied after compression. It does not affect the amount of compression. Workflow tip: first adjust Peak Reduction to reach the desired compression (watch the gain reduction meter), then adjust Gain until the output matches your mix.

• Try parallel compression

  Many modern LA-2A plugins (like Waves and UAD) include a mix knob, making parallel compression easy. Set the plugin to compress heavily (8–10 dB gain reduction), then bring the mix knob down to 30–50%. This blends compressed and dry signals, giving consistency without flattening dynamics. If your plugin lacks a mix knob, create a parallel aux channel, insert the LA-2A there, and blend it with the dry track.

• Add EQ after compression

  The LA-2A can slightly smooth transients, which may darken the signal. Fix this by inserting an EQ after the plugin and applying a gentle high-shelf boost (1–2 dB around 3–5 kHz for vocals, higher for instruments). On bass, this can also create a subtle pumping effect, keeping the low end controlled while preserving presence in the mix.

• Decide whether to use analog noise

  Some plugin versions (like Waves CLA-2A) include an “Analog” button that adds noise modeling. This is a matter of taste but can introduce unwanted hiss. For the cleanest sound, keep it off. If you want an “in-the-room” feel, turn it on, but monitor the overall noise floor carefully.

LA-2A Plugin Quick Settings

The LA-2A is known for its smooth, program-dependent attack and release, so you don’t get traditional attack/release knobs. Instead, you control it mainly with Peak Reduction (how much compression) and Gain (makeup gain). Here are some practical starting points. These aren’t rules! Use them to listen and learn what the LA-2A is doing, and then tweak to fit your track:

Source	Mode	Peak Reduction	Gain	Extra Tips
Vocals	Compress	Set for 3–5 dB reduction	Raise until output matches mix	Use UAD’s Gray model for smooth vocals, or Waves CLA-2A for brighter presence. Stack after an 1176 for extra control.
Bass	Limit	4–7 dB reduction	Adjust until bass sits steady	Limit mode holds bass levels tight. Add a gentle high-shelf EQ after to restore clarity if needed.
Acoustic Guitar	Compress	2–3 dB reduction	Adjust by ear	Light compression keeps strums even without flattening dynamics. UAD Silver model is slightly faster and works well here.
Electric Guitar	Compress	3–5 dB reduction	Adjust as needed	Great for smoothing out sustained notes. Try IK White 2A for a balanced tone, or Waves CLA-2A if you want more bite.
Drum Bus	Limit	5–7 dB reduction	Blend back with mix knob	Use plugins with mix controls (UAD, Waves) for parallel compression. Adds consistency without killing punch.
Mix Bus	Compress	1–2 dB reduction	Subtle gain lift	Keep it light. Use UAD’s Mix control to dial in parallel compression for glue. Avoid heavy limiting on the full mix.