The NUX METAL CORE DELUXE MKII is a high gain preamp pedal with 3 distinctive high gain amp models including the Duo Rect, Fireman, and VH 4. You can select these models via the 3-way toggle switch. The Duo Rect is based on the Mesa Boogie Dual Rectifier. The familiar 90’s American metal sound with the iconic metal front panel that reminds you of countless classic records, from metal to punk to grunge, including Metallica, Tool, Korn, Soundgarden, Foo Fighters and Blink 182. The Fireman is based on the Friedman BE-100, the man behind the signature tones of rock icons including Eddie Van Halen, Steve Stevens, and Jerry Cantrell. For over a decade the "BE" circuit has been hailed as the epitome of British tone. Ampless & Impulse Responses. Impulse Responses play an important parts when it comes to going ampless, as it gives you that cabinet sound to complete your tone quest. Each of the included amps on the METAL CORE DELUXE MKII have a matching IR to go sonically along with it. You can load your own favorite 3rd party IRs via the MetalCore editing software. Please visit the product page and download the editor (METAL CORE DELUXE MKII supports 512 samples IR resolution.). The MetalCore editing software will convert the IR file automatically, just make sure that your IR file is in WAV format. USB The USB-C port is for firmware updates and connecting to the MetalCore editing software (see below). To update the pedal, connect a USB cable to your PC and hold the footswitch to boot-up the device and to enter the DFU (Device Firmware Update) mode. Once connected you can perform firmware updates using DFU updater software. USB The USB-C port is for firmware updates and connecting to the MetalCore editing software (see below). To update the pedal, connect a USB cable to your PC and hold the footswitch to boot-up the device and to enter the DFU (Device Firmware Update) mode. Once connected you can perform firmware updates using DFU updater software.