“Dazzlingly authentic speaker and miked room tones that truly sound and feel like guitar speaker cabinets”: UAFX OX Stomp Dynamic Speaker Emulator review

It's the Ox in a 'box, offering the same studio-quality cab and mic emulation in a compact, pedalboard-friendly format

Universal Audio OX Stomp
(Image: © Universal Audio)

Guitar World Verdict

The UAFX OX Stomp allows guitarists to enjoy UA’s world class Dynamic Speaker Technology with their favorite amp modelers or even “real world” amps (via a reactive load box or line out) in an easy-to-use stomp box format ideal for the stage and studio


  • +

    Vast selection of speaker cabs.

  • +

    Studio-quality post effects.

  • +

    Easy to use on stage or in studio.

  • +

    Dynamic responsiveness and authentic room ambience.


  • -

    UAFX Control app Bluetooth connection can be unreliable. Unbalanced outputs may require DI box in some applications.

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In my previous review of UAFX stomp boxes, I mentioned how Universal Audio was bringing the sounds of classic studio gear to the stage. 

The company's new OX Stomp pedal also brings studio-quality sound to the stage, but this time around, UA has adapted modern software processing instead of classic hardware, harnessing the power of the company's outstanding Dynamic Speaker Modeling technology in a stomp box format. OX Stomp also provides effects like 1176 compression, reverb, delay, modulation and more to provide complete, studio-polished sounds.

OX Stomp is basically the rig section (speaker/room/mic emulation and effects) of UA’s OX Amp Top Box – in other words, OX without the reactive load box, headphone amp, digital connections, etc. 

OX Stomp’s pedal format allows users to configure a pedalboard fly rig with an amp emulation pedal like the UAFX Lion ’68, Dream ’65 and so on, or various other companies’ units, but it’s also great to use in the studio with an amp head and your favorite reactive load box, an amp’s line out (with speaker load), or to upgrade or provide alternative speaker emulation for amp modeling hardware and software. 

However, even though it’s a stomp box, it’s not really designed to be used going into a standard amp rig – you can do that and get good sounds, but to hear OX Stomp at its best you’ll want to use it with full-range studio monitors, FRFR cabs, or a stage PA system.

Universal Audio OX Stomp

(Image credit: Universal Audio)

With 22 different speaker emulations ranging from 1x10 and 1x12 cabs to various 4x12 cabs, six cab mics/six room mics (condenser, dynamic, ribbon), and four simultaneous stereo effects (four-band EQ plus low/high cut, 1176 compression, delay with modulation effects like flanger or chorus, and reverb), OX Stomp provides everything your guitar signal needs for post-amp studio polish.

Users can configure custom rigs that store all of those features’ settings, and six rigs are instantly accessible via a rotary switch on the pedal’s top panel. OX Stomp stores up to 1,000 rigs internally, and rigs are assigned to the pedal’s rig selector via the UAFX Control app for iOS and Android devices. 

Other top panel controls include Room for adjusting room ambience, Speaker Drive for adjusting dynamic responsiveness from tight to distorted cone cry, Output (overall output level), and separate Mic 1 and Mic 2 knobs that adjust the level of the corresponding mics. Mic Select toggle switches for Mic 1 and 2 select Dynamic, Condenser, or Ribbon mic models. Rear panel jacks include pairs of TS ¼-inch stereo inputs and outputs and a USB C connector for downloading software updates.

UA’s Dynamic Speaker Emulation truly lives up to its name by providing dazzlingly authentic speaker and miked room tones that truly sound and feel like guitar speaker cabinets.

I preferred the sound of OX Stomp to the IRs in several expensive amp modelers I own, and especially loved using OX Stomp in a mix-and-match rig with my favorite classic tube heads and Suhr Reactive Load box. The EQ, 1176, delay/modulation and reverb effects are all first class and add an alluring finishing touch for studio sound perfection – these effects are worth the pedal’s price alone. 

Universal Audio OX Stomp

(Image credit: Universal Audio)

Users have mentioned problems with Bluetooth connections between the OX Stomp and mobile devices with the UAFX Control app. Installing both the latest operating system and updated version of the software should eliminate most problems.

I preferred using the app on a tablet device, which made it easier to set up rigs and adjust various parameters. The factory rigs provided with OX Stomp are so good that you may never need to tweak or program your own.


Universal Audio OX Stomp

(Image credit: Universal Audio)
  • PRICE: $399 
  • TYPE: Speaker cabinet and mic emulation pedal
  • CONTROLS: Room level, Speaker Drive, Output, Mic 1 mini-toggle switch, Mic 2 mini-toggle switch, Mic 1 level, Rig selector, Mic 2 level, 2x footswitches
  • FEATURES: EQ, 1176 compression, plate reverb, stereo delay and modulation; dynamic, ribbon, and condenser mic emulation, room emulation
  • POWER: 9V DC (400mA)
  • CONTACT: Universal Audio

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Chris Gill

Chris is the co-author of Eruption - Conversations with Eddie Van Halen. He is a 40-year music industry veteran who started at Boardwalk Entertainment (Joan Jett, Night Ranger) and Roland US before becoming a guitar journalist in 1991. He has interviewed more than 600 artists, written more than 1,400 product reviews and contributed to Jeff Beck’s Beck 01: Hot Rods and Rock & Roll and Eric Clapton’s Six String Stories.