The Universal Audio UAFX Knuckles, sold as the Knuckles '92, is a digital DSP preamp pedal that models the 1992 Mesa/Boogie Dual Rectifier Revision F amplifier12. It is an amp simulation pedal with cabinet emulation, built around UA's dual-engine processing, and it packs all three Dual Rectifier channels, Clean, Orange and Red, into a stompbox2. Guitar Pedal X describes it as a take on "the famous 1992 Rev F Dual Rec high-gain amplifier tone that fueled punk, alt rock, and metal from the '90s onward"1.
It is the fourth in Universal Audio's series of legendary amps as pedals, following the Lion, Anti, and Enigmatic, and Guitar Pedal X calls it essentially the second of the company's High Gain Preamp pedals after the ANTI 5150 take13. The pedal launched on 22 October 2024 and was available immediately3.
A 1992 Dual Rectifier preamp in a pedal
The Knuckles '92 is based on the Revision F version of Mesa's high-gain Dual Rectifier2. All three of the Dual Rectifier's channels are present: Clean, Orange and Red2. Guitar Pedal X lists the channel control as Clean, Original and Red1.
Alongside the amp modeling, the pedal includes a secondary overdrive with three controls, which Guitar Pedal X identifies as a TS808-style circuit, plus a 3-band EQ with Presence and a Gate1. Gearnews reports that UA promises tones spanning "the guitar sound of Rock legends like Incubus or the Foo Fighters just as much as the piercing leads of Nevermore or Dream Theater"3.
The pedal also carries six cabinet emulations. Three are pre-installed2:
- UK V30: 4x12 British cab with Vintage 30s32
- CA V30: 4x12 oversized American cab with Vintage 30s32
- White 75: 4x12 British cab with Celestion 75s32
Registering the pedal unlocks three more, exchangeable with the originals via the UAFX app: a 1x12 EV12, a 4x12 with Celestion 80s, and a 4x12 Brown3.
The controls
The control set is Gain, Presence, Output, Bass, Mid, Treble, three mini-toggle switches and two footswitches, an On footswitch and a Preset footswitch12. The Gain knob has a Room control on an inner ring for ambience level1.
The middle toggle switch is a utility selector with three positions: Amp, Alt and Store13. In Amp mode the knobs control the amp model. In Alt mode the knobs take on secondary roles: Gain sets ambience level, Presence becomes the threshold for the noise gate, and the EQ section handles the secondary overdrive's gain, tone and level2. In Store mode you can change and store presets3.
The pedal operates in one of two modes, Live or preset, with Live engaged by the On footswitch working as what-you-see-is-what-you-get2.
Power and connections
The Knuckles '92 runs on an isolated 9V DC supply, center-negative, with a 400 mA minimum draw12. Guitar World notes the supply is not included with the pedal2.
At 400 mA minimum, the Knuckles '92 needs more current than a typical compact analog pedal. It requires an isolated 9V DC output rated for at least 400 mA, and the supply is sold separately12.
Connectivity is stereo throughout: two 1/4" TS inputs and two 1/4" TS outputs, with the right input and right output used for stereo connections and 4-cable mode, plus USB-C and Bluetooth12. The enclosure is die-cast with metal switches and plastic rotary controls2. Sources differ on the dimensions: Guitar World lists 90 x 42 x 14 mm and a weight of 21 oz (604 g)2, while Guitar Pedal X lists 9.2 x 14.1 x 6.5 cm and 0.567 kg1.
A firmware 2.0 update in November 2025 added MIDI compatibility, four onboard presets switchable on the hardware, improved Bluetooth and a USB-to-Mobile connection option across the compatible UAFX pedal range2. Presets can also be handled through the UAFX mobile app, including tones designed by UA's tone gurus, dual-rec specialists and artists1.
What reviewers said
Guitar Pedal X's reviewer found the modeling impressive, writing that "the modelling here is about as good as it gets for the current state of the art" with minimal latency1.
Guitar World's review was more emphatic about the sound:
"In over 20 years of hardware and software modeling, this is hands-down the best-sounding emulation of Mesa's shiny high-gain model."
Guitar World's verdict overall was of excellent sounds from the pedal2. Gearnews, covering the launch, noted the Knuckles "might tick even more boxes (or cabs) than its three predecessors Lion, Anti, and Enigmatic"3.
Videos
Andertons Music Co
Universal Audio
Rabea Massaad
Questions
Is the UAFX Knuckles stereo?
Yes. It has two 1/4-inch TS inputs and two 1/4-inch TS outputs, with the right input and right output used for stereo connections and 4-cable mode. Guitar World also lists stereo inputs, stereo outputs, USB-C and Bluetooth among its connectivity.
Can you save presets on the UAFX Knuckles?
Yes. After the UAFX firmware 2.0 update in November 2025, players can store four presets on the pedal and switch between them on the hardware. Presets can also be managed through the UAFX mobile app, which includes tones designed by UA's tone gurus, dual-rec specialists and artists.
What power supply does the UAFX Knuckles need?
It needs an isolated 9V DC supply, center-negative, delivering at least 400 mA. The supply is sold separately and is not included with the pedal, so a typical low-current daisy chain will not run it.
Which Mesa Boogie amp is the Knuckles modeled on?
It models the 1992 Mesa/Boogie Dual Rectifier Revision F. Guitar Pedal X describes it as a take on the Rev F Dual Rec high-gain tone that fueled punk, alt rock and metal from the '90s onward, with Clean, Original and Red channels.
Does the UAFX Knuckles support MIDI?
Yes, since the firmware 2.0 update released in November 2025, which added MIDI compatibility to the Knuckles '92 and other compatible UAFX pedals, along with four onboard presets and improved app connectivity.
Does Knuckles '92 come with a power supply?
No. The pedal requires a supply capable of delivering 9V at 400 mA and it is not included in the box, so you need to buy one separately.
Sources (3)
- Guitar Pedal X, Guitar Pedal X, 2024-10-23
- Universal Audio UAFX Knuckles '92 Dual Rec amp pedal review, Guitar World, 2024-11-13
- UAFX Knuckles '92: Mesa your Boogie, gearnews.com, 2024-10-22
