Electrodyne BAC-500 Fet Compressor 500 Series

From the top down, the BAC’s faceplate features a large silver rotary input knob, smaller pots for attack, release and ratio, and a large output knob at the bottom. Additional features include a three-position sidechain contour switch, eight-LED gain reduction meter, and pushbuttons for distortion and bypass.

The module’s attack control runs from fast to quite fast, while the release control exhibits a fairly wide range, enabling the compressor to go from “pumping, breathing fast” up to approximately a second and a half. This allows sounds to “hang” a bit when using the device purely as a leveler or limiter.

The ratio control features five positions ranging from 2:1 to 20:1, with a sixth position marked as “∞!”. According to Avenson, “The infinity control has a little exclamation point next to it because, not only is it really flat, but it also puts you in that spot where you can do some over-compression and other interesting things. It changes where the threshold starts to compress as well, so it gives you different varieties of tonal characteristics to play with.”

The BAC’s sidechain toggle switch offers a choice of three possible settings: flat, high-pass filter (cut off around 70 to 100 Hz), and an option that somewhat exaggerates the high end while simultaneously cutting the low end. “The overall effect of this third setting is somewhat like a de-esser fed into the sidechain, but it’s a little wider than that and quite good for taming a variety of things that are overly bright,” Avenson notes.

With all of the controls essentially cranked between the input and output knobs, the BAC is capable of delivering nearly 50 dB of gain, which can be very helpful in compensating for serious gain reduction issues caused by greatly compressing dynamic range.

The bypass button found below the output knob is a true relay bypass, while the adjacent distortion button allows the user to achieve a true bench FET compression sound. “A lot of FET compressors use tricks to linearize the FET as a compression element and make it sound cleaner because if they’re used solely by themselves, they’re really pretty raunchy sounding,” says the designer. “So this switch allows you to play with how much of the frequency response and distortion characteristics of the FET you get. By engaging it, you’re getting a lot more second harmonic distortion and aggressive sounds because we’re taking away some of the linearizing elements. It’s basically a way to kick in a more aggressive sounding compressor without changing any of the other settings. You can dial in the amount of dirt you want.”

Avenson sums the BAC up by adding, “Although this product is largely designed to provide a bit of color and flavor—and not be too heavy handed—it really does possess that nice ‘bite’ that is characteristic of FET compressors and perfect for cranking down on things like drum room mics when you need it.”