The NUX Metal Core Deluxe MKII is a digital high gain preamp pedal, what NUX calls an "Amp in a box"1. It packs three high gain amp models into a compact enclosure: the Duo Rect, Fireman and VH4, based on the Mesa Boogie Dual Rectifier, the Friedman BE-100 and the Diezel VH4 respectively1. You pick between them with a 3-way toggle switch on the face of the pedal1. RockBoard's PedalPedia classifies it as a distortion, equalizer and preamp pedal in one2.
The three amp models
Each position of the toggle switch selects a different amp circuit, and each is modeled on a well-known high gain head1.
| Model | Based on | NUX's description |
|---|---|---|
| Duo Rect | Mesa Boogie Dual Rectifier1 | "The familiar 90's American metal sound", a front panel NUX ties to records from Metallica, Tool, Korn, Soundgarden, Foo Fighters and Blink 1821 |
| Fireman | Friedman BE-1001 | The "BE" circuit, which NUX says "has been hailed as the epitome of British tone"1 |
| VH4 | Diezel VH41 | "A thick, articulate and 'meaty' sound, that is loved by many players"1 |
The VH4 model traces back to the Diezel amp of the same name, which NUX credits with revolutionizing the industry through its 4-channel design and individual inserts1. The Fireman's BE-100 connection runs through Friedman's work with players NUX names as Eddie Van Halen, Steve Stevens and Jerry Cantrell1. Players who want a standalone distortion pedal rather than a full preamp can also look at NUX's other high gain offerings, such as the NUX Fireman and the NUX NDS-5 Fireman Distortion, or the original NUX Metal Core.
Power and connections
The Metal Core Deluxe MKII runs on 9V DC with a negative tip, using the optional NUX ACD-006A adapter1. Current draw is less than 120mA1, which is modest for a digital preamp but more than a simple analog distortion box, so plan a power supply output that can deliver it. Input impedance is 1MΩ and output impedance is 1kΩ1, standard values that let it sit anywhere in a pedal chain without loading guitar pickups.
The pedal is true bypass1, so when it is disengaged your signal passes through untouched. The IR speaker simulation is controlled separately, at startup: with the pedal not connected via USB, hold the footswitch while plugging in the power supply to toggle whether the IR is engaged or disengaged when the pedal boots1.
Software, IRs and the mobile app
The Metal Core Deluxe MKII connects to NUX's editing software, which lets you tweak parameters and load third-party IRs (impulse responses, the files that simulate a speaker cabinet and microphone). The software is at version 1.0.0 for both Windows and macOS, and the pedal's firmware is at V1.26 for macOS and Windows1.
There is also the EFX Mobile APP for editing from a phone:
- iOS: requires a Lightning to USB adaptor to connect1
- Android: NUX says using an OTG adaptor ensures most Android systems will work with the pedal properly1
For players using the pedal straight into a PA or audio interface, the IR section is what turns the preamp's raw output into a finished cab-simulated tone; loading your own third-party IRs through the software gives you control over that stage1. More on that side of things is on the Speaker Simulation Pedals page.
Where it sits among distortion pedals
As a digital preamp pedal rather than an analog distortion circuit, the Metal Core Deluxe MKII takes a different approach from most boxes on the Distortion Pedals page: instead of clipping your signal with diodes or op-amps, it models complete amplifiers, each with its own character, and adds cabinet simulation on top21. RockBoard's PedalPedia describes it as "a digital distortion pedal designed to deliver ultimate metal tone"2. Players comparing it against simpler analog options, like the NUX Brownie or the NUX DS-3 Classic Distortion, are choosing between one pedal that covers three amp voices plus IRs and pedals that do one thing in an analog signal path.
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Questions
Is the NUX Metal Core Deluxe MKII analog or digital?
It is a digital pedal. NUX describes it as a high gain preamp pedal with three amp models, and RockBoard's PedalPedia listing also lists its circuit type as digital. The three models are the Duo Rect, Fireman and VH4, selected with a 3-way toggle switch.
Is the Metal Core Deluxe MKII true bypass?
Yes. NUX lists the Metal Core Deluxe MKII as true bypass, so with the pedal disengaged the signal passes through without the circuit in the path. The IR cabinet simulation can also be turned on or off independently at startup.
How do you turn the IR on or off at startup?
With the pedal not connected via USB, hold the footswitch while plugging in the power supply to boot the pedal up. This toggles whether the IR speaker simulation is engaged or disengaged when the pedal starts.
Does the Metal Core Deluxe app work on iPhone?
Yes, but iOS requires a Lightning to USB adaptor to use the EFX Mobile APP with the pedal. On Android, NUX says using an OTG adaptor ensures most Android systems will work with the Metal Core Deluxe MKII properly.
What amps is the Metal Core Deluxe based on?
The Duo Rect model is based on the Mesa Boogie Dual Rectifier, the Fireman on the Friedman BE-100, and the VH4 on the Diezel VH4. NUX describes the Duo Rect as the familiar 90's American metal sound and the VH4 as thick, articulate and meaty.
Sources (2)
- Metal Core Deluxe MKII, NUX Audio, 2025-08-05
- Metal Core Deluxe MKII by NUX, RockBoard (rockboard.de PedalPedia), 2026
