DBX 1BX III Dynamic Range Expander with Impact Restoration

The dbx 1BX III is a one-band, single-channel dynamic range expander with features like a true RMS detector, an infrasonic filter, a 10-LED display for monitoring gain change, variable attack and release times, and Impact Restoration to enhance transients. Key specifications include a 1.0 to 1.5 (0 to 50%) expansion ratio, a dynamic range of 110 dB, a 20 Hz to 20 kHz frequency response (±0.5 dB at 1.0 expansion), and a typical 0.1% total harmonic distortion.  

Key Features 
One-Band Expansion: The 1BX III functions as a single-band expander, providing a wide frequency spectrum for audio enhancement.
True RMS Detector: Features a true RMS (Root Mean Square) detector, which accurately measures the overall signal level, not just peaks.
Infrasonic Filter: Includes a 10 dB/octave infrasonic filter at 30 Hz to prevent mistracking from low-frequency noises like turntable rumble.
10-LED Display: Provides visual feedback on both the amount and direction of gain change during the expansion process.
Variable Attack and Release: The time it takes for the expander to react to signal changes (attack) and to return to normal (release) is adjustable based on the program material.
Impact Restoration: This feature is designed to restore the impact and punch of transient sounds.

Specifications 
Expansion Ratio: 1.0 to 1.5 (0% to 50% increase in dynamic range), linear in decibels.
Dynamic Range: 110 dB (peak signal to weighted background noise).
Transition Level (Threshold): Adjustable from 30 mV to 3 V.
Frequency Response: ±0.5 dB from 20 Hz to 20 kHz at an expansion ratio of 1.0.
Total Harmonic Distortion (THD): Typically 0.1% from 20 Hz to 20 kHz at 1.0 expansion.
General 
Type: Dynamic Range Expander.
Release Year: Originally released around 1978.