The BSS DPR-504 is a professional 1U rack-mount 4-channel (quad) noise gate. It is widely used in live sound and recording to eliminate background noise, crosstalk, and hum from signal sources.

• 4 Independent Channels: Each of the four channels includes its own set of controls, though channels can be linked in pairs (1/2 and 3/4) for stereo operation.
• Parametric Key Filter: Each channel has a dedicated frequency-conscious filter to prevent “false triggering” (e.g., keeping a snare mic from opening due to kick drum bleed).
• Key Listen: A momentary switch allows you to listen specifically to the filtered “key” signal to tune the gate with precision.
• Dual Metering: Features simultaneous display of both key signal level and threshold setting on a 12-point LED meter.
• Attack Modes: Includes a “Fast” mode for transients (percussion) and an “Auto” mode that tracks signal dynamics for smoother performance.
• Release/Hold Control: A combined control where the “hold” time tracks proportionally with the release time to ensure natural envelope shaping.