Pete’s Place Audio: BAC-500 Compressor

The BAC—short for Brad Avenson Compressor—is a feedback-style FET compressor built around two discrete op amps and a custom wound output transformer.

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.

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