The NUX MG-400 is a digital multi-effects processor from NUX, a floor unit that puts amp modeling, cabinet simulation and effects in one box. It carries 25 amp models, 25 guitar cabinets and 48 effects models, and ships with 65 patches pre-loaded so you can audition sounds straight away1. NUX positions it as "the best value modeler for the money" and describes it as a unit built around "how working guitarists actually use a multi-effects processor on stage and in the studio"2.
Inside, the MG-400 houses two DSP chips running NUX's White-Box Amp Modeling algorithm (TS/AC-HD) for the amps and Core-Image post-effects for everything after them2. MusicRadar's reviewer Matt McCracken found the amp models "cover everything from classic clean amps based on Fender or more modern amps from Matchless," through classic Marshall emulations to higher-gain Mesa and Bogner models1.
What the MG-400 does
The MG-400 is a multi-effects unit: one floorboard that replaces an amp and a pedalboard for players who want everything in a single box. The signal chain runs through an amp block, cabinet simulation and the effects blocks, with 48 effects models available across them1. The cabinet section offers 25 guitar cabs1.
The amp models span the range most players need. McCracken's review describes classic Fender-based cleans, modern Matchless-style amps, classic Marshall emulations, and higher-gain Mesa and Bogner models1. For players who want to build drive sounds separately, the effects section covers the usual ground, and the unit's 65 pre-loaded patches give you a starting point for each1.
The MG-400 sits in NUX's MG line above the MG-300, which NUX calls its "little brother"2. Guitar World's budget multi-effects guide noted of the MG-300 that "with amp modeling, a plethora of effects, plus custom IR loading, the NUX MG-300 does a lot for relatively little money"6, and the MG-400 carries that approach further with its expression pedal, color screen and dual-engine GEN2 architecture.
The controls
The MG-400 is laid out as a floor unit with footswitches, a built-in expression pedal and a color display12.
| Control | What it does |
|---|---|
| Two preset footswitches | Cycle through presets; the upper switch has a footswitch topper1 |
| Two control footswitches | Select "scenes" within a preset bank, work as looper and jam controls, and activate the onboard tuner when pressed together1 |
| Built-in expression pedal | Rubber-gripped top, debossed NUX logo, at the far right of the unit; hold the PEDAL button to switch it to WAH mode21 |
| TAP key | Tap tempo; hold it for direct BPM input from 40 to 240 BPM, which auto-applies to the current preset's time-based effects2 |
| SELECT knob | Dials in the target BPM in direct input mode2 |
| 2.8-inch color LCD | 320 x 240 display with NUX's UI for editing21 |
The expression pedal doubles as a wah. NUX describes it simply: "Hold the PEDAL button and the MG-400's built-in expression pedal instantly switches to WAH mode"2. On the related MG-300, the expression pedal can control volume or the effects, with a MOD function controlling the mix level of modulation effects7.
GEN2 also adds a Global TAP toggle under SYSTEM MENU, PARA. FOLLOW. When enabled, the TAP BPM syncs across all presets' delay and modulation effects, so one tap sets the tempo everywhere rather than per-preset2.
GEN2 firmware: NAM Loader, Deep Image amps and new WAH types
The GEN2 firmware, released for the MG-400 as version 3.0.3 on 2026/08/28 for macOS, is the biggest change to the unit since launch2. It reworks the AMP block into a dual-engine architecture:
- Deep Image Amp x3: three amp models built on NUX's Deep Image modeling2
- NAM Loader x10: ten slots for loading NAM captures, files made by capturing the sound of a real amplifier2
- Dual-engine architecture: the two engines run side by side in the AMP block2
The WAH block expands to 4 types in GEN2, which NUX says covers "the full spectrum from classic Cry Baby character to modern wide-band" styles, with Blues, Funk, Rock and Metal all represented2. The EFX block gains 5 new Deep Image-based effect types, which NUX describes as expanding "your tonal shaping options beyond drive and distortion into new dimensions"2. GEN2 also adds a real-time EQ dB display and the direct BPM input and Global TAP described above2.
The firmware line before GEN2 reached V2.1.1, which added 2 more amps2. NUX also publishes Windows ASIO drivers for the unit, V3.29.0 for Win7 and V5.30.0 for Win10 and above, and the user manual in English, French, German, Italian, Japanese, Russian and Spanish2.
Connections and recording
The MG-400's rear panel carries a 1/4-inch input, stereo 1/4-inch outputs, a 1/8-inch headphone socket, a 1/8-inch aux in and a USB-C port1. The USB-C out carries audio for recording, so the unit works as a USB audio interface into a computer1, with the ASIO drivers above for Windows users2.
Power is 9V DC, center negative, at 280mA3. At that draw the MG-400 needs a proper power supply, not a battery, and it is beyond what a small daisy chain designed for analog pedals will comfortably deliver.
The looper
The looper offers two recording modes. NR (Normal Recording) works as a regular loop function: press the CTRL1 footswitch and it starts recording. AR (Auto Recording) starts recording automatically when you hit the strings, so you do not have to time the footswitch press2. The two control footswitches double as the looper and jam controls1.
What reviewers said
MusicRadar's Matt McCracken reviewed the unit and found it a strong choice for newer players, with some reservations1:
"There are some small niggles but for a beginner guitar player, there's not much wrong with the NUX MG-4001."
McCracken also noted it "offers plenty of high-quality guitar tones if you're willing to tweak"1.
On price, the MG-400 lists at $229 USD4. MusicRadar gives the same dollar figure with £199 and €195 alongside it5, while Guitar World's listing gives €229 for the EU4.
Videos
Guitar World
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NUX Vietnam
Questions
Can the NUX MG-400 load NAM captures?
Yes. The GEN2 firmware gives the MG-400 a dual-engine AMP block with a NAM Loader holding 10 slots, alongside three Deep Image amp models. NAM captures are files created from real amplifiers, so you can load captures of your own amps into those slots.
How do I update the NUX MG-400 to GEN2 firmware?
NUX publishes firmware downloads on the MG-400 product page. The GEN2 release for macOS is version 3.0.3, dated 2026/08/28, and the earlier V2 line reached V2.1.1. The page also lists NUX ASIO drivers for Windows, V3.29.0 for Win7 and V5.30.0 for Win10 and above.
Can the NUX MG-400 be used as a USB audio interface?
Yes. The MG-400 has a USB-C port that carries audio out for recording, so it works as a recording interface into a computer. NUX provides ASIO drivers for Windows on the product page. The unit also has stereo 1/4-inch outputs and a 1/8-inch headphone socket.
Does the NUX MG-400 have a looper?
Yes. The looper has two recording modes: NR (Normal Recording), which works as a regular loop function when you press the CTRL1 footswitch, and AR (Auto Recording), which starts recording automatically when you hit the strings.
What is the difference between the NUX MG-300 and MG-400?
NUX describes the MG-400 as a value-packed modeler akin to its little brother, the MG-300. The MG-400 adds a built-in expression pedal with a WAH mode, a 2.8-inch color LCD, and two control footswitches for scenes, the looper and the tuner. Both offer amp modeling and effects.
Sources (7)
- NUX MG-400 review, MusicRadar, 2024-04-17
- MG-400 - NUX Audio, NUX Audio (nuxaudio.com), 2026-07-10
- MG-400 by NUX, RockBoard PedalPedia, 2026
- Nux MG-50Li review, Guitar World, 2026-05-02
- "An unholy amount of features in a standard-sized compact pedal": Mooer Prime Minimax M2 Intelligent Pedal review, MusicRadar, 2025-04-24
- Best budget multi-effects pedals: a world of effects, Guitar World, 2022-09-27
- MG-300 - NUX Audio, NUX Audio, 2026-04-08
