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Universal Audio OX Reactive Amp Attenuator with Speaker Modeling , $1,499.00 - Add to Cart Skip to Product Information

Universal Audio OX Reactive Amp Attenuator with Speaker Modeling

Reactive Load Box and Speaker Emulator for Tube Amplifiers
Universal Audio OX Reactive Amp Attenuator with Speaker Modeling
Universal Audio OX Reactive Amp Attenuator with Speaker Modeling
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Free Paradise Guitar Studio Software, a $199 Value!
Purchase this item at Sweetwater and receive Paradise Guitar Studio Software for free, a $199 value! Your free plug-in will be delivered upon registration. Software must be registered with Universal Audio by 9/30/2026. Download the Rebate Form

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Universal Audio OX Reactive Amp Attenuator with Speaker Modeling
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A More Flexible Way to Use Your Tube Amplifier

This article was Written By

Our Product Research Team

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With the Universal Audio OX Amp Top Box, you can play your favorite tube amplifier at its sonic sweet spot at any volume level. And that's just the start — featuring UA's Dynamic Speaker modeling technology, you'll be able to access dozens of spot-on mic and guitar cabinet emulations. Premium analog components and one of the world's best reactive load circuits ensure you'll hear all the dynamics and harmonic complexity your amplifier has to offer. The OX Amp Top Box is a powerful solution for recording, allowing you to achieve those cranked-amp tube tones at any volume level. Many recording guitarists at Sweetwater prefer this recording method for maximum sonic control. Instead of a speaker cabinet, plug your tube amp into the Universal Audio OX Amp Top Box to explore a whole new range of tonal possibilities.

What's New for Firmware v1.2

A free firmware update tops off your OX with the latest speaker models and artist RIGs (presets) from Universal Audio, as well as some live-ready amp and footswitch support. Here's what's included:

Five new speaker cabinets

  • 4x12 UK Vee 30 — A modern closed-back cabinet with four 12" speakers; great for heavy, distorted, and scooped amp tones.
  • 4x12 CA Vee 30 — This vintage closed-back 4x12 cabinet is one of the industry standards for rock and metal.
  • 4x12 GB 30 — A basketweave closed-back cab whose 30W "green" speakers exhibit loads of definition and a tight bass response.
  • 2x12 JBF 120 — Punch and articulation in a late ’60s-era cabinet; perfect for loud and clean tube amps, especially within the realm of country, surf, and psychedelic rock.
  • 1x12 JBG 125 — Loaded with a rare speaker that found favor with most famous boutique amp builders of the ‘70s and ‘80s; similar to the JBF 120, but warmer overall.

27 RIGs inspired by legendary stage and studio tones

Universal Audio's latest RIGs pay tribute to some legendary tones by the likes of Eric Johnson, the Beatles, the Grateful Dead, Kansas, Metallica, Steve Vai, Mark Tremonti, Deep Purple, Pat Metheny, John Frusciante, and more.

Expanded footswitch control

In addition to the expanded tones, the latest firmware also gives you hands-free control over the OX's onboard FX using your 1-, 2-, or 3-button footswitches.

Solid-state amp support

OX has proven itself with tube amps. Now it's time to put its solid-state amp support to the test. Just be sure to check your amp's output rating so as not to exceed the OX's maximum input power handling of 150W RMS.

Reactive load circuit for realistic speaker response: no cabinet required

Universal Audio claims OX features the best reactive load circuit in the world, allowing you to crank up your amp for harmonically-rich tone while keeping volume at practical levels. Reactive load circuits respond to your amp's signal the same way a real speaker cabinet would. That means you'll hear — and feel — all the sonic nuance and harmonic complexity your amplifier has to offer, even when you're playing at neighbor-friendly volumes. Or even through headphones. You'll feel like you're playing through a real speaker cabinet because the reactive load responds the same way — and Sweetwater is sure that will inform your playing for the better.

Accurate speaker breakup and cone cry sets OX apart

Because OX is a reactive load box, it responds in a complex and non-linear fashion to the signal you're sending it from your amp — just like a real speaker cabinet does. That means you can achieve realistic "cone cry," which is the generation of additional harmonics in a speaker cone that occurs only at certain frequencies and volume levels. And you'll hear lifelike speaker breakup as you crank your amplifier, even when OX is keeping the volume at bedroom levels. Not only will you hear these sonically-sweet complexities, you'll feel them as OX responds to the nuances of your personal playing style.

The ultimate recording tool for guitarists?

With dozens of microphone and guitar cabinet emulations to choose from, OX offers a ton of flexibility in the studio. It's like having a world-class microphone placed in the perfect position in front of a premium speaker cabinet, in a great-sounding studio space. Except you don't have to set up a mic, manage acoustic reflections, fight noise, and so on. Just plug in your amplifier of choice, use the Rig control to explore mic and cab combinations, and you're ready to record with stellar tone at any volume level.

Remote control over Wi-Fi with app for Windows, Mac, and iPad

With the OX app for your PC, Mac, or iPad, you have full control over OX's parameters from your local Wi-Fi network. Access key parameters, change mic and cabinet combinations, and much more, from anywhere within Wi-Fi range. Don’t want to carry a computer or iPad to the gig? No problem! UA allows you to load 6 full rigs to the front panel selection switch so you can change from a small combo to a full stack with just a twist. This includes every single, tweaky parameter available within OX’s huge range of control. Note: OX requires a 2.4 GHz Wi-Fi connection (5 GHz bands are incompatible).

Universal Audio OX Amp Top Box Features:

  • Reactive load box for tube amplifiers with built-in speaker emulation
  • Dynamic Speaker modeling emulates the nuanced behavior of real moving speakers
  • Access dozens of mic and guitar cabinet models
  • Allows you to achieve cranked-amp tones at any volume level
  • "Rig" controls elects six customizable mic/cab/FX combinations
  • "Room" controls the ambient room sound of the Rig emulation
  • Footswitch input for additional control options
  • Selectable 4-, 8-, or 16-ohm operation
  • Built-in EQ, compression, delay, and reverb effects
  • Headphone output for silent practice
  • Balanced line outputs and S/PDIF digital output for recording
  • Use Windows, Mac, and iPad apps over Wi-Fi for remote control
  • OX requires a 2.4 GHz Wi-Fi connection (5 GHz bands are incompatible)

Warranty Info

Sweetwater's FREE 2-Year Total Confidence Coverage Warranty

Extra peace of mind at no extra cost.

  • Save money with FREE parts and labor
  • Get back to making music with the industry's fastest turnaround time
  • Fix it the first time with our award-winning, factory-certified Service Department
Learn More about Total Confidence Coverage

Offer applies only to single-receipt qualifying purchases. Select manufacturers may require that only the manufacturer’s products qualify towards the minimum purchase amount needed to be eligible for promotional financing. Otherwise, an invoice that meets the minimum purchase amount and contains at least one qualifying manufacturer product is eligible for promotional financing. No interest will be charged on promo purchase balance, and equal monthly payments are required on promo purchase until it is paid in full. The payments equal the amount financed divided by the number of months in the promo period, rounded up to the next whole dollar. These payments may be higher than the payments that would be required if this purchase was a non-promo purchase. During the last month(s) of the promo period the required monthly payment may be reduced due to the prior months’ rounding. Regular account terms apply to non-promo purchases. New Accounts as of 07/31/2025: Purchase APR is 34.99%. Penalty APR is 39.99%. Min Interest Charge is $2. Existing cardholders: See your credit card agreement terms. Subject to credit approval.

Offer applies only to single-receipt qualifying purchases. No interest will be charged on the promo balance if you pay it off, in full, within the promo period. If you do not, interest will be charged on the promo balance from the purchase date. The required minimum monthly payments may or may not pay off the promo balance before the end of the promo period, depending on purchase amount, promo length and payment allocation. Regular account terms apply to non-promo purchases and, after promo period ends, to the promo balance. New Accounts as of 07/31/2025: Purchase APR is 34.99%. Penalty APR is 39.99%. Min Interest Charge is $2. Existing cardholders: See your credit card agreement terms. Subject to credit approval.

The estimated required monthly payment shown which excludes taxes and delivery equals the amount financed divided by the number of months in the promo period, rounded up to the next cent. During the last month(s) of the promo period the required monthly payment may be reduced due to this rounding. These payments apply only with the financing offer shown. If you make these payments by the due date each month, you should pay off this amount financed within the promo period, if it is the only balance you are paying off. If you have other balances on your account, this payment will be added to any other minimum monthly payments.

Applies only to select items from this manufacturer. Ask your Sweetwater Sales Engineer for more details.