MXR M281 Bass Innovations Thump Bass Preamp

A "tape echo" preamp turned into a sculpting tool for bass

Originally, the Echoplex is associated with the world of tape echoes, but it is its preamp that has marked generations of musicians: a sensation of a "bigger" sound, more alive, with extra definition in the attack. The MXR M281 Thump transposes this spirit to bass and takes it further thanks to an EQ designed for the truly critical areas of the instrument.

Within the MXR range, the Thump stands as a modern and compact tool in the bass-oriented series: a simple-to-use preamp/boost, yet precise enough to adjust a finicky backline, tame a resonant room, or restore character to a passive bass.

For which bassists, styles, and contexts?

The Thump is aimed at bassists who want a clean, solid, and controlled sound, from beginners (quick and effective settings) to experienced musicians (fine EQ, chain placement, mix optimization). It particularly shines in styles where the bass must remain clear: funk, pop, rock, punk, modern metal, gospel, indie, clean studio settings, or live contexts where each venue demands compromises.

On stage, it becomes a formidable "plan B": you can activate it to boost a solo, beef up a too tame signal, or quickly correct an excess of low-mids. In the studio, it serves as a pre-EQ tool before the interface or amp, to lay down a more coherent foundation before compression and final equalization.

Controls, settings, and design: the essentials, in the right place

The MXR M281 Thump goes straight to the point with five controls: Output for overall level, Bass and Treb to quickly shape the low end and attack, Mid to scoop or boost the core of the sound, and especially Freq to precisely select the midrange area to work on. This Mid/Freq pair is key: it allows you to switch from a round, full bass to a bass that "speaks" in the mix, without making the adjustment complicated.

Practically, the mini format fits easily on a pedalboard, and the footswitch allows instant switching between a "foundation" sound and a "spotlight" sound. The true hardwire bypass ensures reliable behavior if you use it for occasional activation, but the Thump can just as well remain always-on as a sound base.

The sound

The character of the Thump is that of a warm and punchy preamp : a sensation of a sharper attack, firmer lows, and clearer presence without harshness if the EQ is kept moderate. With the EQ flat, you get a subtle improvement in "grain" and dynamics, ideal for bringing out a passive bass. Pushing the settings, it becomes a true mixing pedal: you can reinforce impact at 40 Hz, open the highs to better define the pick, or choose the right mid frequency (250 Hz to 1 kHz) to either thicken or make room for guitars.

The pedal responds well to playing: it respects right-hand/left-hand nuances, and its level reserve allows you to drive the input of an amp or another pedal (overdrive, compressor) to gain in feel and articulation.

Technical specifications

Effects	Bass	True bypass	Yes
Technology	Analog	Color	Green
Format	Pedal	Power supply included	No
Inputs	Instrument jack	Power supply	DC 9 V
Outputs	Jack

Type	bass preamp / boost	Input impedance	1 M?
Bypass	true hardwire bypass	Output impedance	100 ?
Bass	+15 / -7 dBV at 40 Hz	Noise floor	-95 dBV
Mid	+/- 16 dBV (frequency adjustable via Freq)	Height	3.5 cm
Treb	+/- 10 dBV at 4 kHz	Width	3.8 cm
Freq sweep range	250 Hz to 1 kHz	Depth	9 cm
Potentiometers	Treb, Mid, Bass, Output, Freq	Weight	130 g
Footswitch	on/off activation	Required power supply	9 V DC (center negative)
LED	activation indicator	Power connector	2.1 x 5.5 mm
Input	1 x 6.35mm mono jack	Consumption	9 mA
Output	1 x 6.35mm mono jack	Battery powered	no