Universal Audio Teletronix LA-2A Leveling Amplifier

Considering the mystique and the high prices being paid for certain vintage professional audio products (Pultec equalizers, Neumann U47 microphones and numerous others) it's no wonder that manufacturers are "recreating" many of them at a breakneck pace. Whether it is an "accurate" or an "in the style of" approach to these replicas, however, almost none of them are true reproductions.
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Considering the mystique and the high prices being paid for certain vintage professional audio products (Pultec equalizers, Neumann U47 microphones and numerous others) it's no wonder that manufacturers are "recreating" many of them at a breakneck pace. Whether it is an "accurate" or an "in the style of" approach to these replicas, however, almost none of them are true reproductions. It seems the designers (usually for good reasons) cannot resist improving on the originals, so most of these pieces are known to be "not exactly" the same and thus to some would-be buyers, rightly or wrongly, "not exactly" as good.
Product PointsApplications: Studio

Key Features: Single-channel, optical compression, VU meter. Near perfect re-creation of original Teletronix LA-2A design.

Price: $2,995

Contact: Universal Audio at 831-466-3737 Web Site
Enter Universal Audio and the Putnam brothers, Bill and Jim. They are sons of the late Bill Putnam Sr., legendary recording engineer, studio owner and designer of many notable pro audio devices. Unlike virtually all other replica products, the Universal Audio LA-2A is an almost identical part-for-part copy of the original. This undeniably purist approach results in all the greatness and all the flaws of the originals.


In the world of compressors, it just does not get much simpler than the Universal Audio LA-2A ($2,995). In fact, next to some low-end, one-slider dbx units (like the 163X) that were made some years back, there is no compressor I know of with fewer controls.

On the Universal Audio Teletronix LA-2A, controls consist of a limit/compress toggle switch, an output gain control, a combination threshold/gain reduction control, a +4 or +10 output/gain reduction meter display switch and a power switch. There is also a front panel trim pot for calibrating the meter's "0" indication when showing gain reduction.

On the back is a sidechain pre-emphasis control that increases the compressor's sensitivity to high frequencies (originally intended for radio broadcast purposes). Most users will never touch this pot though, leaving it at its default wideband setting. The entire front panel, true to the original, is thoroughly vintage looking: large black plastic knobs, big stainless steel toggle switches, a big ol' retro-looking meter and a gray painted faceplate.

The faceplate is hinged to allow access to the innards without removing the unit from a rack. Removing the two screws and lowering the panel buys you a trip on the way-back machine to the pro audio days of yore. Inside this beauty is an obviously handmade feast of point-to-point wiring and discrete components. No chips, no printed circuit boards, just something that will gladden the hearts of those who, like me, still remember the days of their youth spent building hi-fi systems from kits. It is a treat just to open this thing up and look. The tubes, transformers (three of them; input, output and power) and optical attenuator module all protrude directly off the back of the unit.

The design of the LA-2A is simple, but in its day it was quite advanced. It uses an electro-luminescent panel (similar to a certain type of night light, of all things) and a photoelectric cell to control compression. As the audio input signal increases in level, the electro-luminescent panel glows brighter and the photoelectric cell "looking" at it decreases in resistance.

The innate characteristics of the panel and cell contribute to the unique compression behavior of the unit. Compared to other incandescent light-based devices in its time, the electro-luminescent panel design of the LA-2A was a step forward because it has an inherently faster attack time.

Release time-wise, the cadmium-sulfide photocell reacts in a two-stage manner, initially releasing halfway in about 60 milliseconds. The remainder of the release time varies depending on how long and how far into compression the unit has been driven. Simply put, the longer the time and/or the further the extent into compression the unit is driven, the slower the release will be. This makes a significant contribution to the LA-2A's characteristic sound.

The choice of "compression" or "limiting" available with the toggle switch is described in the manual as being largely a matter of ratio. It is my impression that even in limit mode, the unit is not what would normally be referred to as a brick wall- type limiter - just a fairly high-ratio compressor. Specific ratios are not given, but my guess is that "compress" might be about 3:1 and "limit" might be more like 10:1 (The manufacturer says that in Limit mode the compression ratio is maintained up to a certain point wherein the ratio will increase until it becomes a 'brick wall.' Pushed beyond that point compression will disengage.). Interestingly, the nominal output level is +10 dBm, not +4 as is the more modern convention. Stereo linking to a second LA-2A is available though barrier strip connectors on the back panel.

In Use

The LA-2A in the modern era has been generally known as something of a specialty device, not a "compressor for all occasions," if you will. It most decidedly has a sound, and if you are looking for transparent compression that otherwise leaves the signal as pristine as possible, this is not the box for you.

For an initial evaluation, I patched one channel of a mixed stereo program through the unit (with the threshold set all the way up so there would be no compression) and a gain-matched straight wire alongside it into my console for an A/B test of the unit's sound coloration. As expected, there is plenty of it. It added low-end warmth and reduced top end high-frequency "air." Some upper midrange presence was added as signal level was increased. This appeared to be mainly in the form of mild, euphonic distortion. Mild distortion at all signal levels also gave the sound a certain "blended" quality. On mixed program material this is generally not a good thing.

What I do recommend this wonderful compressor for is single-track instrument or vocal compression. I found where it works best on vocals is when a certain blending or warming of the sound is desired. Since the unit is not exactly clean, its strength is in applications where its coloration enhances the desired effect. This is especially true for particular voices (often female) that are a bit "edgy" or harsh. The LA-2A is like honey in your tea in these cases - smoothing, softening and, yes, warming the sound. The nice thing is that it accomplishes this colored effect without sounding like anything heavy-handed has been "done" to the sound; it effortlessly does its magic without taking away any of the apparent fidelity. On the contrary, the euphonic coloration adds a sort of depth and dimension that can actually make voices sound more hi-fi, in seeming contradiction to the fact that one might know it is doing so partly by means of mild distortion.

With certain preamps and/or certain singers however, the mellowness of this unit can be too much of a good thing. With a Neve 1073 mic preamp for example, on certain (more often male) voices, the LA-2A can be too soft sounding, to the point of murkiness. In these cases I switched to my other trusty UA product, the 1176LN, and the problem was solved. The 1176LN, in comparison to the LA-2A, is a brighter, more transparent, open-sounding compressor. The 1176LN also has quite a bit faster attack time. Like many other optical compressors, the LA-2A is not as fast as might be desired in some cases, allowing brief transients to pass on certain vocal performances.

In other applications the LA-2A is a bit more of a sure thing, especially with electric instruments. In a session involving a bass overdub, the LA-2A sounded just sensational, again providing a certain "blended" quality to the sound but not at the expense of clarity or dynamic impact. It is hard to be definitive in the absence of a vintage unit for a direct A/B comparison, but my sense is that this reissue is better than the older units I have used over many years in various studios; a bit more open and effortless sounding, providing the desired color without as much of a dulling effect.

For a mix of a pop rock track in Pro Tools, using the LA-2A inserted on electric guitar was even more of a no-brainer. I will not repeat the list of adjectives I have already worn out at this point because all the nice things I said about the unit in other scenarios apply for electric guitars at least as much if not more. If you often compress electric guitars, buy an LA-2A and you can thank me later.


As part of a well-equipped studio, this unit is simply indispensable and will sonically complement other compressors in the rack beautifully. Getting the authentic vintage sound with the reassurance of all brand new parts inside is like having your cake and eating it too.