The dbx 166XL is a professional 3-in-1 dynamics processor designed to control and shape audio signals. It combines a compressor/limiter and noise gate in a single rack-mounted unit, making it useful for live sound, recording, broadcasting, and studio mixing.

• Compressor: Reduces the dynamic range of an audio signal by controlling peaks and making the overall level more consistent. It is useful for vocals, bass, drums, guitars, and other instruments.
• Limiter: Prevents audio peaks from becoming excessively loud, helping protect equipment and reduce clipping or distortion.
• Noise Gate: Reduces unwanted low-level noise by attenuating the signal when it falls below a selected threshold. This is particularly useful for reducing microphone bleed, amplifier noise, and stage noise.
• Stereo or dual-mono operation: The two channels can be used independently or linked for stereo processing.
• Controls: Provides adjustable threshold, ratio, attack, release, and output gain, giving you control over how aggressively the signal is processed.
• OverEasy compression: dbx's OverEasy characteristic provides smoother, more musical compression when desired.

In short: the dbx 166XL is a versatile dynamics processor that helps make audio more controlled, consistent, clean, and protected from excessive peaks, while also reducing unwanted noise.