The MXR M87B Blackout Series Bass Compressor is a special edition version of one of MXR's most popular bass pedals, marking 15 years of MXR Bass Innovations. It is a bass compressor pedal with a RATIO knob that steps through four compression ratios, from gentle 4:1 compression up to 20:1 hard limiting, and an OUTPUT knob that sets the overall effect volume. The Blackout edition features a stealthy matte black housing with gloss black text and a bright yellow LED1.
Controls
| Control | What it does |
|---|---|
| FOOTSWITCH | Toggles effect on/bypass; the yellow LED indicates on1 |
| RATIO knob | Selects the compression ratio: 4 selects 4:1, 8 selects 8:1, 12 selects 12:1, 20 selects 20:11 |
| OUTPUT knob | Controls overall effect volume1 |
The RATIO settings cover a wide range of jobs. At 4:1, if the input level rises 4 decibels above threshold, the output level is reduced accordingly, which is the gentlest setting on the knob. Moving up, the manual describes the 12 setting as producing soft limiting, while the 20 setting produces hard limiting, and even "brick wall" limiting with the fastest attack and release settings1.
Power and bypass
The M87B runs on 9 volts DC. It can be powered by one 9-volt battery or by a 9-volt AC adapter such as the Dunlop ECB003/ECB003EU, or an MXR Brick Series power supply. Current draw is 14 mA with the LEDs off, 19 mA with the LEDs on, and 6 mA in bypass1.
To install or replace the battery, remove the bottom plate of the pedal1.
Bypass is true bypass, so the compression circuit is out of the signal path when the effect is off1.
Where it sits in the MXR bass range
MXR builds a wide line of bass pedals alongside the M87B, including the MXR Bass Compressor, the compact MXR Dyna Comp Bass Compressor, the MXR M81 Bass Preamp, the MXR M82B Bass Envelope Filter and the MXR Blackout Series Bass Envelope Filter, which shares the Blackout series treatment. For more on how compression works and where a pedal like this fits on a board, see Compressor Pedals and Bass Pedals.
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Questions
Is the MXR M87B true bypass?
Yes. According to the owner's manual, the M87B Bass Compressor uses true bypass, so when the effect is off the pedal passes your signal without the compression circuit in the path. The yellow LED indicates when the effect is on.
Does the MXR M87B Blackout take a battery?
Yes. The manual states the pedal is powered by one 9-volt battery. To install or replace it, you remove the bottom plate of the pedal. It can also run from a 9-volt DC adapter such as the Dunlop ECB003/ECB003EU or an MXR Brick Series power supply.
What compression ratios does the MXR M87B offer?
The RATIO knob offers four settings: 4:1, 8:1, 12:1 and 20:1. The 4 setting selects a 4:1 ratio, 8 selects 8:1, 12 selects 12:1 and 20 selects 20:1, so you can dial from gentle compression up to heavy limiting.
How do I install a battery in the MXR M87B?
Remove the bottom plate of the pedal to reach the battery compartment, then fit one 9-volt battery as described in the owner's manual.
What is the input impedance of the MXR M87B?
The manual lists the input impedance at 1 megohm, with an output impedance of 600 ohms.
Can the MXR M87B act as a limiter?
Yes. The manual describes the 12 setting as producing soft limiting and the 20 setting as producing hard limiting, including brick wall limiting when the fastest attack and release settings are used.
Sources (1)
- M87B.pdf, Jim Dunlop (jimdunlop.com), 2023
