3BX II

About the 3BX II

The dbx 3BX Series II (3-BX II) is a three-band dynamic range expander designed to restore dynamic range lost in recording, broadcasting, or duplication, giving playback a more natural, live quality. It divides the audio spectrum into three independent bands (low, mid, high) and expands each band separately using RMS detection and voltage‑controlled amplifiers, so loud bass notes do not artificially raise midrange or treble content and midrange peaks do not pull high‑frequency detail unnaturally forward. Expansion amount is user‑adjustable up to roughly 50%, with front‑panel controls for expansion ratio and transition (threshold) level, plus LED bar‑graph indicators showing activity in each band. The unit includes source/tape and pre/post switching for flexible integration with tape decks and other components, and also provides noise‑reduction benefits on analogue sources by lowering the noise floor during quiet passages. Introduced around 1982 as the successor to the original 3BX, the Series II is widely regarded for its ability to expand complex program material with minimal audible artifacts, improving impact and ambience to bring the character of live music closer to the listening room.