Zoom B1X FOUR Bass Multi-Effects Processor with Expression Pedal
The B1X FOUR is the expression pedal version of Zoom's B1 FOUR bass multi-effects unit. It carries more than 70 effects and amp models in one floor pedal, and adds a treadle so the sound can move with your foot.
- Expression pedal: the X in the name. Assign it to volume, wah, delay or pitch and control the effect in real time.
- Over 60 effects: traditional and boutique bass sounds including octaver, bass synth and fuzz.
- 9 amp and cabinet models: classic bass rigs for recreating an on-stage sound.
- 5 effects at once: chain up to five blocks and store the result in one of 50 user patches.
- 68 drum patterns: a built-in rhythm section in 4/4, 3/4 and other time signatures.
- Looper: stack a riff and play over the top of it while you write.
- ZOOM Guitar Lab: free software for downloading extra effects and for managing and backing up patches.
- Still growing: BitCrush arrived in February 2026 and DynaDelay in April 2026.
- Power: 4 AA batteries or the ZOOM AD-16 9V DC adapter, with a Micro-B USB port for the computer connection.
The B1X FOUR is the expression pedal version of Zoom's B1 FOUR bass multi-effects pedal. Everything the standard model does is here, plus a treadle you can assign to volume, wah, delay or pitch, so a parameter moves with your foot instead of sitting fixed for the whole song.
Effects and amp models
There are more than 70 effects and amp models on board. The effects side runs to over 60 traditional and boutique bass sounds, including octaver, bass synth and fuzz, and up to five of them can run at once in a chain. Nine amp and cabinet emulations sit alongside for recreating an on-stage rig. Fifty user patch slots hold your own chains, which means a set list can be stepped through in order rather than rebuilt between songs.
Practice tools built in
A drum machine with 68 rhythm patterns in 4/4, 3/4 and other time signatures gives you something to lock to, and the looper lets you lay down a part and play over it. For a bass player working alone at home, that pairing covers most of what a practice session needs without another box on the floor.
Guitar Lab and ongoing updates
ZOOM Guitar Lab is the free companion software for the B1 FOUR series. It downloads additional effects, builds and edits patches on a larger screen, and backs the whole library up. Zoom has kept adding to it, with BitCrush released in February 2026 and DynaDelay in April 2026, so the pedal on the shelf today holds more than the one that first shipped.
Connections and power
A standard mono jack takes the bass in and a stereo mini AUX input lets you play along with a phone or media player. Conversion is 24-bit with 128x oversampling at 44.1 kHz and internal processing is 32-bit. Power comes from 4 AA batteries, rated at around 18 hours of continuous use on alkalines with the backlight off, or from the ZOOM AD-16 9V DC adapter. The USB port is Micro-B.