This pedal combines the tone-sweetening magic of the Echoplex® Preamp with a three-band EQ and midrange frequency adjustment so that you can dial in the perfect bass tone to punch up a solo, boost your signal in a live mix, sculpt more edge into the sound of a passive bass, and more.

This pedal can be powered by a Dunlop ECB003 9-volt adapter, or the DC Brick™, Iso-Brick™, and Mini Iso-Brick™ power supplies (not included).

• Echoplex preamp that’s tailored to bass guitar
• 3-band EQ enables you to tweak 40Hz and 8kHz
• Midrange is adjustable from 250Hz to 1kHz for maximum tonal flexibility
• Great for punching up solos, boosting your live signal, and adding an aggressive edge to passive pickups

THE LONG STORY

The MXR Thump Bass Preamp is a tone-sweetening, signal-boosting, and altogether groove-enhancing machine. This pedal was conceived when the MXR design team and our in-house bass players discovered that the Echoplex® Preamp’s sonic secret sauce made for just as delectable a pairing with bass as it does with guitar. Using that circuitry as a foundation, the MXR team added a simple yet potent tone-shaping interface so that you can dial in the perfect bass sound for the stage and the studio.

Crafting the sound you need is easy. The Echoplex Preamp circuit conditions your signal with a carefully balanced EQ profile, and this pedal’s tone controls let you take it from there. The Treble and Bass knobs cut or boost frequencies at 4 kHz and 40 Hz respectively, while the Mid knob cuts or boosts the midrange as set by the Frequency knob, from 250 Hz to 1 kHz. This range of frequencies was selected to give players maximum flexibility and minimal fuss when refining their bass signal.

Whether you need to punch up a solo, boost your signal in a live mix, or sculpt more edge into the sound of a passive bass, the Thump Bass Preamp packs incredible versatility into an MXR mini housing.

CONTROLS

1. OUTPUT knob sets output level of effect
2. TREBLE knob boosts or cuts high end frequencies at 4 kHz
3. MID knob boosts or cuts midrange as set by FREQUENCY knob
4. BASS knob boosts or cuts bass frequencies at 40 Hz
5. FREQUENCY knob sets midrange frequency from 250 Hz to 1 kHz
6. FOOTSWITCH toggles effect on/bypass (blue LED indicates on

DIRECTIONS

• Run a cable from your instrument to M281’s INPUT jack and another cable from M281’s OUTPUT jack to your amplifier.
• Start with all controls at 12 o’clock.
• Turn the effect on by depressing the footswitch.
• Rotate OUTPUT knob clockwise to increase volume or counterclockwise to decrease it.
• Rotate TREBLE knob clockwise to boost high end frequencies or counterclockwise to cut them.
• Rotate FREQUENCY knob clockwise for a higher midrange frequency center or counterclockwise for a lower midrange frequency center.
• Rotate MID knob clockwise to boost midrange frequencies or counterclockwise to cut them.
• Rotate BASS knob clockwise to boost low end frequencies or counterclockwise to cut them.

SPECIFICATIONS

• Input Impedance 1 MΩ
• Output Impedance 100 Ω
• IMPEDANCE
• TONE CONTROLS
• Bass + 15/-7 dBV, 40 Hz
• Mid ±16 dBV, 1 kHz 
• Treb ±10 dBV, 4 kHz 
• Freq Sweep 250 Hz to 1 kHz
• Noise Floor -95 dBV
• Bypass True Hardwire
• Current Draw 9 mA
• Power Supply 9 Volts DC