Mxr MB301 Bass Synth

The MB301 Bass Synth is an MXR bass synth pedal featuring a main oscillator with three different waveforms, secondary oscillators, an envelope filter, a low-pass filter, and modulation. Designed in collaboration with bassist Ian Martin Allison, this pedal offers a wide range of synth sounds with precise tracking and high sustain. It includes 8 recallable presets with a dedicated button.
OVERVIEW OF THE MXR MB301 BASS SYNTH
The MXR MB301 Bass Synth is a bass pedal that offers vintage analog sounds with a wide range of monophonic synth sounds reminiscent of hits by Stevie Wonder, Michael Jackson, Parliament Funkadelic, and more. Designed in collaboration with bassist and sound connoisseur Ian Martin Allison, this pedal features a sub-octave section, an expressive envelope filter, and rich modulation effects, all with precise tracking and high sustain. The controls are easy to use, designed for detailed sound shaping. The SUB MIX knob adjusts the amount of low octave mixed with the main synth signal. The MOD knob adds liquid and brilliant modulation, ranging from subtle movement to psychedelic pulses. The ENVELOPE control governs the response of the envelope filter. The MIX knob adjusts the blend of clean and affected signal, the CUTOFF control sets the filter's cutoff frequency, and RESONANCE amplifies it for a more impactful sound. Finally, the VOICE button adds harmonically tuned oscillators for more complex sounds, while the SHAPE button allows selection of the main synth signal waveform: triangle, sawtooth, or square.
The MXR MB301 Bass Synth comes with eight pre-loaded presets, designed by Ian Martin Allison. Each preset is inspired by classic synth sounds, such as those heard in Michael Jackson's "Thriller," Herbie Hancock's "Chameleon," Peter Gabriel's "Sledgehammer," and Nine Inch Nails' "Head Like a Hole." To cycle through presets, simply press the PRESETS button.
The Bass Synth offers a range of advanced parameters, including oscillator and modulation mix, compression, and tracking modes. The pedal can be used in stereo mode, paired with an external switch like the MXR Split + Tap or the Tap Tempo Switch to scroll through presets, or use a volume pedal like the Dunlop Volume (X) to blend different sound configurations.
MXR MB301 BASS SYNTH CONTROLS
VOICE: adds additional harmonically tuned oscillators for more complex sounds
CUTOFF: sets the cutoff frequency of the 4-pole resonant low-pass filter
MIX: adjusts the mix between clean signal and synth signal
SUB MIX: adjusts the mix between the main synth signal and sub signals
SHAPE: selects the oscillator waveform: triangle, sawtooth, or square
ENVELOPE: controls the attack and decay time of the envelope filter; lower values offer a fast attack and quick response, while higher settings create a slow effect; setting the knob fully to the left deactivates the envelope filter
MOD: sets the amount of modulation
RESONANCE: increases gain at the cutoff frequency, adding a more expressive and biting effect at higher settings
PRESETS: allows cycling through the 8 internal presets
SECONDARY PARAMETERS
Holding down the VOICE or SHAPE buttons while adjusting other controls allows access to alternative parameters. Parameters accessible by holding the VOICE button relate to the synth patch sound. Each can be saved to a preset and controlled with an expression pedal. Parameters accessible by holding the SHAPE button are mostly utility settings rather than effects. None of the latter can be controlled via an expression pedal. Some of them are global parameters and affect all presets.
Press and hold the VOICE button
MIX knob - VOICE MIX Parameter: with the VOICE button pressed, the MIX knob adjusts the VOICE MIX parameter. Sets the mix between the main oscillator and additional oscillators when the VOICE function is active; at minimum, additional oscillators are removed from the signal:
SUB MIX knob - NOISE MIX Parameter: with the VOICE button pressed, the SUB MIX knob adjusts the NOISE MIX parameter. Sets the mix between the oscillator and noise.
CUTOFF knob - FILTER ENVELOPE AMOUNT Parameter: with the VOICE button pressed, the CUTOFF knob adjusts the FILTER ENVELOPE AMOUNT parameter. Sets the direction and amplitude of the envelope filter (controlled by the ENVELOPE knob). Beyond halfway, the envelope opens the filter; below halfway, it closes the filter for a "ducking" effect.
RESONANCE knob - GLIDE Parameter: with the VOICE button pressed, the RESONANCE knob adjusts the GLIDE parameter. Adjusts the time taken to transition from one note to another for a legato effect.
ENVELOPE knob - AMP ENVELOPE Parameter: with the VOICE button pressed, the ENVELOPE knob adjusts the AMP ENVELOPE parameter. Sets the fade-in (or attack) time of each note.
MOD knob - MOD BLEND Parameter: with the VOICE button pressed, the MOD knob adjusts the MOD BLEND parameter. Sets the mix between chorus and LFO filter modulation.
Press and hold the SHAPE button
MIX knob - COMPRESSION Parameter: with the SHAPE button pressed, the MIX knob adjusts the COMPRESSION parameter. Sets the amount of compression, from no compression to tight, "punchy" compression. Affects how the synth responds to playing intensity.
SUB MIX knob - OUTPUT GAIN Parameter: with the SHAPE button pressed, the SUB MIX knob adjusts the OUTPUT GAIN parameter. Adjusts output gain +/- 18 dB, with 0 dB at the halfway point.
CUTOFF knob - GATE SENSITIVITY (GLOBAL) Parameter: with the SHAPE button pressed, the CUTOFF knob adjusts the GATE SENSITIVITY (GLOBAL) parameter. When playing, the pedal automatically determines the average signal level. This parameter adjusts the pedal's responsiveness when the input signal is lower than this level. The default sensitivity is designed for most situations and playing styles, but dynamic playing or legato works better with high sensitivity. Please note: a note's sustain is independent of the set sensitivity. The note will ring out for as long as it is played on the instrument.
RESONANCE knob - TRACKING (GLOBAL) Parameter: with the SHAPE button pressed, the RESONANCE knob adjusts the TRACKING (GLOBAL) parameter. Determines how the synth signal responds to the instrument's frequency range to ensure accurate note tracking.
5-STRING BASS: default, knob fully to the left. Tracks from a low B to a high C on a 24-fret 6-string bass.
4-STRING BASS: knob at 12 o'clock. Has a faster response than 5-STRING mode, but only tracks down to a low E.
GUITAR: knob fully to the right. Tracks the range of a standard-tuned 24-fret guitar.
ENVELOPE knob - DRY THRU FX Parameter: with the SHAPE button pressed, the ENVELOPE knob adjusts the DRY THRU FX parameter. When active (knob fully to the right), the clean signal passes through filter, chorus, compression, and gate along with the synth signal. This parameter blends the clean and synth signals more completely, allowing the instrument's natural articulation to emerge when using the MIX knob.
MOD knob - OUTPUT MODE (GLOBAL) Parameter: with the SHAPE button pressed, the MOD knob adjusts the OUTPUT MODE (GLOBAL) parameter. Selects the output signal routing.
MONO: default, knob fully to the left. True bypass.
WET/DRY: knob at 12 o'clock. In this mode, the affected signal is on the left channel (tip) and the clean signal on the right channel (ring). Buffered bypass.
STEREO: knob fully to the right. In this mode, the pedal creates a stereo signal by panning the oscillators and activating a stereo filter and chorus. Buffered bypass.
PRESETS
This pedal features eight different presets (four Green presets and four Red), plus a Live mode, active when the preset LEDs are off. Live mode represents the current knob settings. When a preset is modified from how it was saved, its LED will flash slightly.
GREEN PRESETS
THRILLENGANES: inspired by Greg Phillinganes' ARP 2600 sound on Michael Jackson's "Thriller," this low-octave sound suits both '80s hits and contemporary music.
WONDERFUL: based on Stevie Wonder's left-hand sound on the TONTO synth, it offers resonant funk sounds.
LIZARD SYNTH: modeled after Herbie Hancock's ARP Odyssey on the famous "Chameleon," this sound increases resonance for a '70s funky timbre.
SYNTHADELIC: open sound with octaver, based on Bernie Worrell's Minimoog tone on "Flashlight."
RED PRESETS
SLEDGE: inspired by Tony Levin's bass sound on Peter Gabriel's "Sledgehammer," this preset offers the classic analog octave sound with generous use of compression and chorus. Playing with a pick maximizes the potential of this sound.
ARMY OF SYNTH: modeled after the iconic synth bass line on Bjork's "Army of Me." Use an expression pedal for greater intensity.
NINE INCH SYNTH: based on Trent Reznor's synth programming and tone on "Head Like a Hole," this sound is perfect for both rock and dance.
SYNTHMAU5: inspired by the sidechain technique used in electronic music production, this preset brings in the dark atmospheres used by producer deadmau5. Playing precisely on the beat with a quarter-note kick drum makes it seem as if the kick drum hit triggers the bass notes.
Cycling through presets
You can cycle through presets using the dedicated button next to the LEDs, or an external switch like the MXR Split + Tap connected to the CTR jack, in addition to the integrated footswitch. When using an external switch, pressing once cycles forward through presets, while holding it down reverses the scrolling direction. To use the integrated switch, hold it down until the main LED begins to flash. At this point, pressing the footswitch will cycle forward. The SHAPE button LED will flash to indicate the active preset. Hold the switch down again to exit preset selection mode or wait for the scroll menu to time out.
Saving a preset
To save the current settings to a preset, you must first copy the settings by holding down the preset button for 2 seconds. The preset LEDs will flash for confirmation. Then, scroll through the preset bank to select the position where you want to save the preset. Hold down the button again for two seconds to copy the settings to that bank. The preset LEDs will stop flashing. To exit the copy/save menu without saving, simply change the knob settings or wait for the timeout. Please note: you cannot save a preset in Live mode.
Resetting a preset to default settings
To reset a preset to default settings, cycle through the presets to select the one to reset. Then, hold down the footswitch and the preset button simultaneously for 5 seconds. The preset LEDs will flash quickly to confirm the reset. In Live mode, all preset LEDs will flash green after a reset.
Factory reset
Hold down the VOICE and SHAPE buttons simultaneously for 5 seconds when powering on the pedal to perform a factory reset. Once the reset is complete, the Bypass LED will flash quickly several times.
EXPRESSION
Live mode and each preset can store their own expression state. To set the expression behavior of a preset, adjust all parameters in both the heel-down and toe-down positions of the expression pedal according to the desired settings. Then, move the expression pedal through its full range to confirm the desired behavior. Once the expression pedal settings are verified, follow the steps in the "Saving a preset" section. Note that the heel-down state also corresponds to the preset's state when no expression pedal is connected. In Live mode, expression states are saved automatically and maintained as long as the expression pedal remains connected. If the unit is powered on without an expression pedal connected, the next time the pedal is connected, the heel position will be set to the current Live mode state. Note that each time Live mode is entered, the current settings are represented by the knob states until the expression pedal is operated. Changes to expression settings in Live mode will not be recorded until the pedal is physically operated after entering Live mode.
CTR JACK
Expression/Tap Input
Set the CTR side switch to the TAP/EXP position (towards the OUT jack) to use the CTR jack with an expression pedal via a TRS cable or an external switch via a patch cable to cycle through presets.
Audio Output
Set the CTR side switch to the AUDIO position (towards the CTR jack) to use the CTR jack as the right channel of the audio output. In this configuration, use two TRS cables in the OUT and TRS jacks or one TRS cable in the OUT jack to use the pedal in stereo mode.
MXR MB301 BASS SYNTH TECHNICAL SPECIFICATIONS
Input Impedance: 1 MΩ
Output Impedance: 100 Ω
Maximum Input Level: +5 dBV
Noise Floor: -97 dBV
Current Draw: 330 mA
Power Supply: 9 volt DC