Exploring Logic Pro X's Compressor Circuit Types

Logic Pro's built-in compressor has a lot of sound shaping potential below the surface. Joe Albano reveals the ins and outs of its circuit types.  
The Logic Compressor.

The Logic Compressor.

The Logic Compressor, at first glance, is a fairly standard processor. All the usual controls are there, and there's even an extra stage, a separate Limiter, at the output. But there's an almost hidden extra that gives this plug-in a great deal of added flexibility and nuance of sound quality.

The Logic Compressor's Circuit Types.

The Logic Compressor's circuit types.

A few years back,  Apple, with little fanfare, slipped in a Circuit Type pop-up menu. This added to the traditional bread-and-butter Compressor behavior (Platinum), by offering the ability to mimic the characteristic response of various classic hardware compressors. Had they re-skinned the GUI with photorealistic images suggestive of these well-known models, this new feature would have undoubtedly made a bigger splash when it was introduced.

In the world of vintage hardware compressors, there are three main circuit types, and the Logic Compressor does them all. In addition to its original, generic compressor design'"Platinum'"it simulates Optical Compression (Vintage Opto), FET-based compression (Vintage FET), and VCA-based compression (Vintage VCA). Besides these classic models, there are additional, more specific models labelled Studio FET and Studio VCA. None of these claim to be a circuit-by-circuit clone of original analog hardware, as some plug-ins do, but they do promise the essential response and character of those designs. The Studio models are rumored to be based on particular hardware units, though no definitive word has ever come down from Logic's designers.

Opto Compression

In the hardware world, the dean of opto compressors is the Teletronix LA-2A, known for its warm sound, thanks to the all-tube design, and its smooth, transparent compression, thanks to a circuit that uses an internal optical (light-based) assembly that controls detection and gain-reduction. 

The Teletronix LA-2A Opto Compressor.

The Teletronix LA-2A Opto Compressor.


The Logic Compressor Vintage Opto Mode.

The Logic Compressor Vintage Opto mode.

Opto designs are many engineers' go-to models for vocal compression, and the Vintage Opto model offers up that kind of response'"transparency is the word here. Besides vocals, opto compression is great for bass, and any track that you want to compress without having the processing be especially noticeable. A soft-knee setting would undoubtedly provide a response closer to the original circuitry, where the response characteristic actually varied with incoming signal levels'"one of the 'secret ingredients'

Joe is a musician, engineer, and producer in NYC. Over the years, as a small studio operator and freelance engineer, he's made recordings of all types from music & album production to v/o & post. He's also taught all aspects of recording and music technology at several NY audio schools, and has been writing articles for Recording magaz... Read More

Discussion

BenB
YES! Love these LPX articles that have really useful information. I always wondered about those circuitry choices. Now it is clear, and I can really tweak out my mixes really well. GREAT article! Bravo!
Matt Denton
Somewhere around Logic Pro X 10.1 they did reskin these different circuit types with attractive faces so you can see the difference between studio and vintage, for instance, once you get away from the (underrated) Platinum circuit. Great article, thanks!
Joe A
Thanks, guys! Back before the re-skinning I'd always felt that if the Logic Compressor had a fancier graphic people wouldn't be so quick to dismiss it in favor of fancier third-party plug-ins. Now, with the new look making it clearer what circuit types are being emulated, I'm sure it gets more of the attention it deserves, even though the models are the same (except for the new dbx-style model, which is a welcome addition)..

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