Universal Audio OX Amp Top Box

Sale price$ 1,499.00 Regular price$ 1,874.00
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Universal Audio OX Amp Top Box


Universal Audio OX Amp Top Box

The TEC award-winning Universal Audio OX Amp Top Box is a recording system that provides a reactive load for a tube amp combined with physical cabinet and microphone models, letting you record studio quality guitar sound in your home studio

If you want to get a huge guitar sound, you have to push air, which means recording in a room at high volume. But what if you don’t have a treated acoustic space? Or perhaps you have neighbors to consider. Then there’s the issues of miking a cabinet properly along with having the right mics, preamps, and so on. What’s a budding young guitar overlord on a sonic quest to visit musical mayhem on an unsuspecting populace to do? Universal Audio has got your back with the OX speaker and mic modeling amp attenuator. Not only does the UA OX provide a resistive load for your tube amp in place of a speaker for silent recording, it physically models the behavior of a speaker so that it interacts with your amp the way you expect when playing through a real cabinet. Plus, you also get Universal Audio’s world-class dynamic models of microphones and studio spaces to complete the sonic picture. With the UA OX, you can have record-quality guitar tones without leaving the house. No wonder it walked away with a TEC award at NAMM 2019.

Universal Audio OX Amp Top Box—Unique Features:

  • Play and record your tube amp in its tonal sweet spot—anywhere, at any volume, with full dynamics
  • Get stunning mic and guitar cabinet combinations at the turn of a RIG knob—no miking required
  • Audition, tweak, and save more than 100 jaw-dropping custom Rigs from compatible iPad or Mac
  • Get authentic “edge of destruction” sounds, complete with UA Dynamic Room Modeling, speaker breakup, and cone cry

 Universal Audio OX Amp Top Box—Just the Facts:

  • 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 knob
  • Get record-ready sounds quickly with expertly-placed virtual mics and cabs — no amp miking needed
  • Five finely-tuned guitar amp attenuation levels, from off 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 OX mobile or desktop app over Wi-Fi for editing and saving Rig presets
  • Fan-less design for silent operation

Universal Audio OX Amp Top Box—Under the Hood

An exceptional 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. OX is 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 using an impulse response for a static representation of an isolated audio event, OX's physical modeling reacts just like a speaker would, such as cleaning up when you back off on the guitar’s volume; breaking up when you push it harder; or producing “cone cry*” at certain pitches. 

*PAD Fun Fact—Cone Cry is an audible low-frequency harmonic generated by a speaker’s diaphragm pushed beyond the ability of its damping factor to return it to a state of inertia. The diaphragm continues to move after the signal stops, which produces a resonant frequency, or “overhang.” In poorly designed systems, the resonant frequency of the system can produce the phenomenon of “one note bass.” At extreme SPL, rather than its normal piston-like action, a rippling effect is produced across the surface of speaker cone, which has various zones of pitch, much like a steel drum. Based on the physical makeup of the speaker, these pitches, which are not associated with the input note, will resonate. It follows, that not every speaker will “cry” at the same frequencies. And, as Frankie Valli of the Four Seasons informed us, “Big speakers do cry.” (Or maybe it was girls. We thought it was speakers.)   

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 has a variety of connections for all kinds of recording and live work flows. 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.

Power attenuator

The reactive load safely attenuates (soaks) a tube guitar amp’s high-power speaker output so the amp’s power tubes can be pushed to where they sound and feel best.

When a guitar speaker is optionally connected, the amp’s attenuated signal can be delivered to the speaker at different levels so the amp’s high-volume output can be heard at lower volumes. Five carefully crafted volume levels are available. The speaker can also be turned off for silent operation.

Tip: OX’s reactive load includes a safety feature. When power is off, OX presents a 16 ohm load at the "From Amplifier" input to prevent tube amp damage that could occur with an unloaded amp output.

OX software app

OX includes free software for Mac and iPad (OX registration required). With the OX software application, OX Rigs can be wirelessly accessed, modified, and stored with OX’s built-in Wi-Fi networking.

The OX app provides access to all Rig and Room settings, allowing you to create a near-infinite variety of complete guitar tones and store hundreds of Rig presets. 100 carefully crafted default Rigs provide a wide variety of album-quality tones, or use the default Rigs as a starting place for your own custom tones.

With the OX app, you can easily assign different Rigs to the OX’s six Rig knob slots, for access to your favorite Rigs when the OX app is not being used. Rig Sets can be easily assembled to quickly assign a batch of six Rigs to OX’s Rig knob slots for standalone stage and studio use.

The app can control OX by pairing directly to its built-in Wi-Fi hotspot, or by connecting both OX and the Mac or iPad to an existing Wi-Fi network.

OX app features:

  • Full control of OX Amp Top Box rigs via Wi-Fi on iPad or Mac
  • Over 100 rig presets for instant album-quality guitar tones
  • Select from 17 classic speaker cabinets with vintage, NOS, and modern speakers
  • Choose from eight boutique direct mics and six room mic combinations
  • Create, manage, and save your own Rigs to OX hardware for standalone use
  • Perfect your studio amp tones with EQ, compression, delay, and plate reverb

OX app system requirements:

  • OX Amp Top Box
  • Apple Mac or iPad
  • iPad: iOS 11
  • macOS: Sierra or High Sierra

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

Note: Operating systems not listed above are untested. Although untested operating systems may work, they are not supported by Universal Audio.

The Universal Audio OX Amp Top Box lets you record studio quality guitar tone with unlimited variety any time, anywhere. Order yours today. For more information, call or chat online with your PAD Studio Specialist.



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: 1⁄4" Female TS Unbalanced
  • Input Impedance: 4/8/16 ohm (selectable)
  • Maximum Input Power: 150 Watts RMS, 200 Watts RMS peak
  • Safety Load (power off): 16 ohm

Speaker Output

  • Connector Type: 1⁄4" Female TS Unbalanced
  • Output Attenuation: Five Attenuation Steps and Speaker Off
  • Output Latency: None (pure analog)

Line Outputs 1 – 2

  • Connector Type: ⁄4" Female TRS Balanced
  • Dynamic Range: 114.5dB (A-weighted)
  • Frequency Response: 20Hz–20kHz, ±0.1 dB
  • Signal-to-Noise Ratio: 114dB (A-weighted)
  • Total Harmonic Distortion + Noise: -110 dB @ -3dBFS
  • Channel Separation: 129dB
  • Output Impedance: 100 ohm
  • Maximum Output Level: 20.2dBu (balanced)
  • Output Latency: 2.77 milliseconds (122 samples @ 44.1kHz)

Stereo Headphone Outputs

  • Connector Type: 1⁄4" Female TRS Stereo
  • Dynamic Range: 113dB (A-weighted)
  • Frequency Response: 20 Hz–20 kHz, ±0.1 dB
  • Signal-to-Noise Ratio: 113dB (A-weighted)
  • Total Harmonic Distortion + Noise: -107dB @ -3dBFS
  • Maximum Output Power: 80mW into 600 ohms
  • Output Latency: 2.77 milliseconds (122 samples @ 44.1kHz)

Digital Outputs

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


  • Power Supply: External AC to DC Power Supply, Level VI compliant
  • AC Input Connector Type: IEC Male
  • AC Requirements: 100V–240V AC, 50–60Hz
  • 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

Physical (dimensions approx.)

  • Width: 15" / 381.25 mm
  • Height, chassis only: 4-15/32" / 112.94 mm
  • Height, including rubber feet: 5-15/32" / 138.44 mm
  • Depth, chassis only: 8-3/64" / 204.5 mm
  • Depth, including knob & jack protrusions: 9-3/64" / 229.58 mm
  • Shipping Box (W x D x H): 20-/4" x 12-15/16" x 11-5/16" (52.7 cm x 32.9 cm x 28.7 cm)


  • Unit only: 14.1 lb. / 6.40 kg
Package Contents      
  • 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







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