In perfect working order.

The MXR M87 Bass Compressor is an analog studio-style compression stompbox featuring Constant Headroom Technology (CHT) and full parameter controls in a compact Phase 90-sized enclosure. You can explore official details on the Dunlop Product Page.

Controls

• Input: Sets the signal level hitting the compressor to determine the compression threshold.
• Output: Adjusts the makeup gain for your output volume level.
• Attack: Controls how fast the compressor clamps down, ranging from 20 µs to 800 µs.
• Release: Controls how quickly the compression lets go, ranging from 50 ms to 1.1 s.
• Ratio: A rotary or toggle switch offering 4:1, 8:1, 12:1, and 20:1 (where 20:1 acts as a hard limiter).
• Meter Display: A 10-segment LED gain-reduction meter that visually tracks your compression activity.

Technical Specifications

• Input Impedance: 1 MΩ
• Output Impedance: 600 Ω
• Max Input: +14 dBV
• Max Output: +8.5 to +9.2 dBV
• Frequency Response: 20 Hz to 20 kHz
• Max Gain: 31 dB
• Bypass: True hardwire bypass
• Power Requirements: 9V DC center negative adapter or a 9V battery (current draw: ~14 mA with LEDs off, ~19 mA with LEDs on, ~6 mA in bypass)
• Dimensions: Approx. 2.12" x 2.62" x 4.37" (5.9 cm x 11 cm x 4.7 cm including knobs)
• Weight: Approx. 0.56 lbs (239 g)