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Quick answer: The OX - Amp Top Box is an authentic Universal Audio UAFX product. Priced at $1499.00, sold brand-new by Victory Musical Instruments, a veteran-owned authorized UA dealer in Miami, FL. Questions? Call 844-687-4208.
Get legendary studio tones from your tube amp — anywhere, at any volume. The Universal Audio OX Amp Top Box is a premium reactive load box and guitar recording system, letting you crank your tube amp to its sonic sweet spot at any volume — from full band volume to completely silent — while delivering studio-miked tones via UA's Dynamic Speaker Modeling.
At a Glance
| Brand | Universal Audio |
|---|---|
| Model | OX - Amp Top Box |
| Category | Amp Attenuator |
| Form factor | Stompbox / pedal-format |
| Price | $1499.00 |
| SKU / MPN | OX |
| Condition | New (factory sealed) |
| Warranty | Full Universal Audio manufacturer warranty |
| Sold by | Victory Musical Instruments — veteran-owned authorized UA dealer, Miami FL |
Overview
A tube amp sounds best when it's pushed — but pushing a 100-watt Marshall or 50-watt Twin Reverb is impractical in a home studio, apartment, or hotel-room session. The OX Amp Top Box solves this with a premium reactive load box that absorbs the amp's full output, letting you play at sweet-spot volume internally while attenuating the audible output to anywhere from "completely silent" to "full band volume." Combined with UA's Dynamic Speaker Modeling (the same technology in OX Stomp), you get studio-miked tones — speaker, microphone, room — direct to your interface, headphones, or PA.
Key Features
- Premium Reactive Load Box — Your tube amp sees OX as an actual speaker cabinet with continuously variable impedance, preserving tone and feel regardless of attenuation level.
- Five Attenuation Levels — Completely silent, whisper-quiet, bedroom, club, full band volume.
- UA Dynamic Speaker Modeling — Emulates speaker drive, breakup, and cone cry; far beyond static IR loading.
- Front-Panel Six-Position "Rig" Control — Instant recall of six complete cab + mic + room + effects setups.
- Built-In Studio Effects — UA EQ, compression, delay, and reverb.
- Headphone Output — Silent practice with cranked-amp tone.
- Balanced Stereo TRS Line Outputs — Direct to interface or PA.
- S/PDIF Digital Output — RCA and ADAT (TOSLINK), 16-bit / 44.1 kHz.
- Selectable Impedance — 4-, 8-, or 16-ohm operation.
- Wi-Fi Control — Pair with the OX mobile or desktop app for deep editing and preset management.
- Tube Amp Support up to 150W RMS — Handles most popular tube amp heads and combos.
How OX Differs from OX Stomp
OX Amp Top Box is the original UA product — a reactive load box and speaker emulator designed to take the speaker output from a tube amp and convert it to line level, with cab/mic emulation. OX Stomp is the cab/mic/room emulation portion only, in a pedal form factor, for line-level signals — it cannot accept amp speaker outputs. If you have a tube amp and want to record/play silently, get OX Amp Top Box. If you have an amp modeler (UAFX, Kemper, Helix, etc.) and want better cab/mic emulation, get OX Stomp.
Use Cases
- Silent Studio Recording — Track tube amps at full volume into headphones or direct to interface, with no microphone setup required.
- Apartment / Home Studio Practice — Crank your Marshall at midnight without disturbing anyone.
- Live Direct-to-FOH — Bypass mic setup entirely; deliver consistent studio-miked tone direct to the front-of-house mixer.
- Reamping — Send pre-recorded DI tracks back through a real amp and capture via OX.
Specifications
- Amp Input Power — Up to 150W RMS (tube amps only; solid-state amps that exceed 150W can damage OX)
- Speaker Impedance — Selectable 4 / 8 / 16 Ω
- Attenuation — Five levels from silent to full band volume
- Outputs — Balanced TRS stereo, S/PDIF (RCA + ADAT TOSLINK), 1/4" headphone
- Digital Resolution — 16-bit / 44.1 kHz fixed
- Connectivity — Wi-Fi (built-in hotspot) for OX app
- Dimensions — 21" x 13" x 12"
- Weight — 20 lbs
Important Note
OX is designed for tube amps up to 150W RMS. Many solid-state amps exceed this rating and can permanently damage OX. Verify your amp's output rating before connecting. Damage from exceeding the 150W input power rating is not covered under warranty.
What's in the Box
- OX Amp Top Box
- IEC power cable
- Quick start guide
- 1-year limited warranty
Frequently Asked Questions
Is the OX a pedal, a plug-in, or hardware?
The OX Amp Top Box is real analog hardware: a reactive load box and speaker emulator. It connects to your tube amp's speaker output so you can play and record at any volume, with no computer required for the core experience.
Do I still need my guitar amp?
Yes. The OX works with your real tube amplifier, taming and re-amping its output. It is not a standalone amp emulator pedal.
What's included in the box?
Your purchase includes: OX Amp Top Box, IEC power cable, Quick start guide, 1-year limited warranty.
Is the OX - Amp Top Box a genuine Universal Audio product?
Yes. Victory Musical Instruments is a veteran-owned, authorized Universal Audio dealer based in Miami, FL. Every unit is brand-new, factory-sealed, and covered by the full UA manufacturer warranty.
Can I get help choosing or setting it up?
Absolutely. You'll talk to real people, not a call center. Call us at 844-687-4208 and we'll help you spec the right gear and get it running.
Why Buy from Victory Musical Instruments
Victory Musical Instruments is a veteran-owned authorized retailer in Miami, FL. Whether you're outfitting a home studio, a college program, or a worship room, we'll help you spec the right gear and stand behind the sale. Save through our ID.me military discount program — active duty, veterans, reservists, and eligible family.