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Universal Audio OX Amp Top Box

Premium Reactive Load Box



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Product Description

The Universal Audio OX Amp Top Box is a cutting-edge unit, allowing you to get the sweetest tones from your tube amplifiers but at ear-friendly volumes. Essentially an amp load box and attenuator, this amazing piece of gear goes one step further - in typical Universal Audio fashion! 

With many sophisticated features such as dynamic speaker modelling and cabinet emulation, the OX also has a dedicated app to let you really fine-tune your tones. Old-school circuitry meets modern flexibility when it comes to the OX, with UA's boutique analogue quality ensuring that none of your base tone is hindered by digital processing, but rather embellished by the convincing modelling technology.

Key Features

  • Get the ultimate tone out of your tube amp — anywhere, and at any volume
  • Pair your amp to the world's best reactive load, with boutique UA analog quality — built for years of home and studio use
  • Instantly audition dozens of album-quality mic and guitar cabinet setups with front panel "Rig" control
  • Get authentic "edge of destruction" tones complete with speaker breakup and cone cry, thanks to UA Dynamic Speaker Modeling
  • Premium, no-compromise analog reactive load box for tube guitar amps
  • Five finely-tuned guitar amp attenuation levels —  from off, to whisper quiet, to full band volume
  • Front-panel “Rig” control for instant, album-quality mic and speaker cabinet emulations
  • UA Dynamic Speaker Modeling emulates speaker 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 outputs for stereo recording
  • Pair with OX mobile or desktop app over Wi-Fi for editing and saving presets
  • Speaker cables not included

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Get The Most Out Of Your Amp - At Any Volume!

Nothing beats the sound of a real, genuine tube amplifier, but they only sound their absolute best when they're cranked. This is usually fine in most live situations, but if you're playing at home and want all of the tonal goodness from your super-loud Plexi or big Fender combo at a lower volume, it's not achievable. But that's where the OX Top Box comes in...

By plugging your amplifier into the OX, the unit ensures that it is safely loaded, to prevent any damage from occurring without the cabinet. A speaker cabinet can of course be used in conjunction with the OX, and with selectable 4, 8, and 16-Ohm operation, most amplifiers will be compatible. 

The main function of the OX though is its attenuation and modelling capabilities. By attenuating your amplifier, this means that you can turn up the master volume so that all of the rich, harmonic content is brought out for the ultimate tone. Then, you can use the OX's own volume control to monitor the overall output, giving you your favourite amp sound at any volume! 

This not only makes the OX Top Box an incredible tool for home use, but also for studio recording. And with balanced TRS line outs and S/PDIF digital outputs, you can record directly into an interface or mixing desk, and even send the signal directly to front-of-house in stereo for a fuller sound when playing live. It's that flexible! 

Speaker & Cabinet Emulation

UA are renowned for their incredible plug-ins for DAWs, and they've integrated their convincing modelling technology into the OX. Fully accessible via the free OX app, you can choose from multiple speaker and cabinet models, with the former capable of emulating speaker breakup and cone cry for the most genuine tones conceivable.

The cabinet models are also very detailed and accurately matched to their real-life counterparts, letting you find the best pairing for your amplifier. This is another great feature that makes the OX perfect for studio use, as you can easily experiment with your setup to find the optimal tone on-the-fly.

And it doesn't end there, as the OX also boasts mic emulations, with the app letting you even adjust its placement on the simulated cabinets/speakers. And top-quality EQ, compression, delay, and reverb effects are also built into the OX, giving you some essential effects to play around with!

Included in the box

  • OX Amp Top Box Unit
  • External Power Supply
  • IEC Power Cable — US, EU, or UK (region dependent)
  • Quick Start Guide
  • RIG Control Presets
  • Safety & License Sheet

Technical Specifications

I/O Complement

  • Amplifier Input: One
  • Speaker Output One
  • Line Outputs: Two (one stereo left/right)
  • Headphone Output: One (stereo left/right)
  • Digital Outputs: Two (mirrored)

Amplifier Input

  • Connector Type: ¼” Female TS Unbalanced
  • Input Impedance: 4/8/16 Ohms (selectable)
  • Maximum Input Power: 150 Watts RMS, 200 Watts peak
  • Safety Load (power off): 16 Ohms

Speaker Output

  • Connector Type: ¼” Female TS Unbalanced
  • Output Attenuation: Five Attenuation Steps and Speaker Off
  • Output Latency: None (pure analog)

Line Outputs 1 – 2

  • Connector Type: ¼” Female TRS Balanced
  • Dynamic Range: 114.5 dB (A-weighted)
  • Frequency Response: 20 Hz – 20 kHz, ±0.1 dB
  • Signal-to-Noise Ratio: 114.0 dB (A-weighted)
  • Total Harmonic Distortion + Noise: -110 dB @ -3 dBFS
  • Channel Separation: 129 dB
  • Output Impedance: 100 Ohms
  • Maximum Output Level: 20.2 dBu (balanced)
  • Output Latency: 2.77 milliseconds (122 samples @ 44.1 kHz)

Stereo Headphone Outputs

  • Connector Type: ¼” Female TRS Stereo
  • Dynamic Range: 113.0 dB (A-weighted)
  • Frequency Response: 20 Hz – 20 kHz, ±0.1 dB
  • Signal-to-Noise Ratio: 113.0 dB (A-weighted)
  • Total Harmonic Distortion + Noise: -107 dB @ -3 dBFS
  • Maximum Output Power: 80 milliwatts into 600 Ohms
  • Output Latency: 2.77 milliseconds (122 samples @ 44.1 kHz)

Digital Outputs

  • Format: S/PDIF IEC958
  • Connector Type 1: Female Phono (RCA)
  • Connector Type 2: Optical TOSLINK JIS F05
  • Sample Rate & Bit Depth: 44.1 kHz, 24-bit
  • Output Latency: 2.57 milliseconds (113 samples @ 44.1 kHz)


  • Power Supply: External AC to DC Power Supply, Level VI compliant
  • AC Input Connector Type: IEC Male
  • AC Requirements: 100V – 240V AC, 50 – 60 Hz
  • DC Connector Type: XLR 4-Pin Locking Male (Neutrik P/N NC4MDM3-H)
  • DC Requirements: 12 VDC ±5%, 1.5A
  • Maximum Power Consumption: 18 Watts
  • Operating Temperature Range: 32° to 104° Fahrenheit (0° to 40° Celsius)
  • Storage Temperature Range: –40° to 176° Fahrenheit (–40° to 80° Celsius)
  • Operating Humidity Range: 10% – 95%, non-condensing


  • Width 15.01 in / 381.25 mm
  • Height, Chassis Only 4.45 in / 112.94 mm
  • Height, Including Rubber Feet 5.45 in / 138.44 mm
  • Depth, Chassis Only 8.05 in / 204.5 mm
  • Depth, Including Knob & Jack Protrusions 9.04 in / 229.58 mm
  • Weight (unit only) 14.1 Lbs / 6.40 kg
Elliot Stent author picture

Written by Elliot Stent

Customer Reviews


35 reviews





Mr David Cronin17th Dec 2023

Value 4Looks 5Durability 5Sound 5

Mr. Bruce Mason11th Feb 2023

I vpcan play M guitar when my wife is home! Sounds increadible

Value 4Looks 5Durability 5Sound 5

Dr H24th Dec 2022

Previously had a Boss TAE. Both have Pros and Cons. Think they are both equally good for slight different purposes. Doesn’t sound as good as the amp straight into cab obviously!

Value 4Looks 5Durability 5Sound 4

Mr Gary McTeggart7th Jun 2022

Value 4Looks 5Durability 5Sound 5

M F Box21st Sep 2021

Value 3Looks 5Durability 4Sound 5

Mr. Edward Fermor16th Sep 2021

The OX has opened up a whole new world in my approach to recording guitars. Pushing my guitar amps further than ever before has lead me to great new sounds I didn't know I had and the inclusion of some great cabs, mic's and realtime efx are the icing on the cake.

Value 4Looks 4Durability 4Sound 5

Mr Samuel Jordan28th Aug 2021

The Ox, (domesticated bull) exactly what I like my Marshall to be! No sacrifice in the magic at any volume I like. High quality from Universal Audio as always. 5*

Value 3Looks 5Durability 5Sound 5

Mr Michael Michael21st Jul 2021

Fantastic bit of kit. Home recording guitars using my amps, and sound is fantastic, great features. Essential bit of kit. Very easy to use and great sounds immediately.

Value 4Looks 5Durability 4Sound 5

Mr Eduardo Gonzalez2nd Jun 2021

The sound you can get out of this and your good old valve amp is just phenomenal. A breakthrough for the recording industry. Pricey, but wouldn't you pay all the money in the world to get that awesome sound?

Value 4Looks 5Durability 5Sound 5

Clive Kay13th Mar 2021

Value 3Looks 4Durability 5Sound 5

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Andertons Music Company's Registered Office: 58-59 Woodbridge Road, Guildford, GU1 4RF. Andertons Music Company acts as a credit broker and not a lender and only offers credit products from Secure Trust Bank PLC trading as V12 Retail Finance. Not all products offered by Secure Trust Bank PLC are regulated by the Financial Conduct Authority. Andertons Music Company is authorised and regulated by the Financial Conduct Authority, firm registration number 716155. Credit provided subject to age and status.