OX - Amp Top Box

Reactive Load Box and Speaker Emulator for Tube Amplifiers
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Universal Audio
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Get Legendary Studio Tones from your Tube Amp — Anywhere, at Any Volume.

OX is a premium reactive load box and guitar recording system, giving you perfectly studio-miked amp sounds from your favorite tube amp. OX lets you play and record your amp in its sweet spots — from huge clean tones and edge-of-breakup to fully cranked — at any volume level, and with mic,room, and speaker cabinet emulations at the turn of a knob.


Featuring Universal Audio’s breakthrough Dynamic Speake rModeling, OX is the first system to accurately emulate speaker drive, breakup,and cone cry — making it the world’s finest speaker attenuator and guitar amp recording solution.


Play and record your tube amp in its tonal sweet spot —anywhere, at any volume, with full dynamics              

Audition, tweak, and save more than 100 jaw-dropping custom Rigs from compatible iPad, or Mac/Windows computers.

Get stunning mic and guitar cabinet combinations at the turn of a RIG knob — no miking required   

Get authentic “edge of destruction” sounds, complete with UA Dynamic Room Modeling, speaker breakup, and cone cry

The World’s Best Reactive Load Box

With decades of analog hardware engineering expertise,Universal Audio’s dream team of engineers set out to design a reactive load box that retains the tone, dynamics, and feel of your tube amp — no matter how much it’s attenuated. The goal was for your tube amp to “see” OX as an actual speaker — with continuously variable impedance and response — so you don’t lose a drop of tone or playing dynamics.

A Complete Guitar Recording System

OX’s front-panel, six-position RIG control allows you to quickly choose from complete setups — including emulated speaker cabinets,close mics, ambient room mics, and up to four simultaneous studio effects. OXis also the only guitar recording system to offer a complete selection of expertly placed room mics, giving you the authentic experience of pushing air while recording your cranked amp in a world-class tracking room.

Dynamic Speaker Modeling

UA’s groundbreaking Dynamic Speaker Modeling faithfully emulates speaker breakup, drive, and cone cry — an essential ingredient to authentic tube amp tones. Using the Speaker Breakup knob in the OX app, you can control the harmonics and sonic complexity that occurs only at certain frequencies and volume levels on various speakers — far beyond a static Impulse Response system — giving you the same sonic phenomenon that occurs with a real speaker cabinet.

All The Right Connections

Not only does OX Amp Top Box feature a front-panel headphone jack for silent practice with your cranked tube amp, it also sports a bevy of connections for all kinds of recording and live workflows. Stereo S/PDIF digital outputs via RCA and optical TOSLINK, as well as balanced TRS stereo line outputs with front panel level control, give you the necessary connections for studio monitors, DAW, or live mixing console inputs. Plus, you can connect any one, two, or three-button foot switch and toggle OX's studio-quality effects on and off.

A Beautiful Software App

Most guitar products do digital awkwardly. They’re ugly and hard to understand. The OX software app, on the other hand, offers slick,intuitive control over all of OX’s RIG settings via Wi-Fi — letting you tweak,store and recall hundreds of presets from your iPad, Mac, or Windows 10 computer. You can then save your six favorite tones onto OX’s front-panel RIG knob for instant recall in the studio or at a gig.


Premium, no-compromise analog reactive load box and guitar recording system for tube guitar amps


Instant album-quality mic and speaker cabinet tones via front-panel RIG control


Get record-ready sounds quickly with expertly-placed virtual mics and cabs — no amp miking required


Five finely-tuned guitar amp attenuation levels, from completely silent to whisper quiet to full band volume


UA Dynamic Speaker Modeling emulates speaker drive, breakup and cone cry


World-class Universal Audio EQ, compression, delay, and reverb effects built-in


Selectable 4, 8, and 16-ohm operation


Front-panel Headphone out for silent practice with cranked tones


Balanced TRS line outs and S/PDIF digital outs for stereo recording


Pair with the OX mobile or desktop app over Wi-Fi for editing and saving RIG presets


Foot switchable control of OX's studio-quality effects

OX App Requirements

OX Amp Top Box

2.4 GHz Wi-Fi network with internet connection to register (once only)

(iPad) iOS 12 or iPadOS 13

(Mac) macOS Mojave or Catalina

(Win) Windows 10 64-Bit Edition

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