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Universal Audio OX Reactive Amp Attenuator with Speaker Modeling

Reactive Load Box and Speaker Emulator for Tube Amplifiers
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A More Flexible Way to Use Your Tube Amplifier

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)

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Tech Specs

  • Type: Reactive Load
  • Power Handling: 150W RMS
  • Impedance: 4/8/16 ohms
  • Attenuation: 5-way switch
  • Inputs: 1 x 1/4" TS (from amp)
  • Outputs: 1 x 1/4" TS (to speaker), 2 x 1/4" TRS (line/monitor), 1 x Coax (S/PDIF), 1 x Toslink (S/PDIF), 1 x USB Type B, 2 x USB Type A
  • Headphones: 1 x 1/4" TRS
  • Other I/O: 1 x 1/4" (foot control)
  • Features: IR Cab Models
  • Power Source: 12V DC (1.5A) power supply (included)
  • Height: 5.5"
  • Width: 15"
  • Depth: 9"
  • Weight: 14.1 lbs.
  • Manufacturer Part Number: OX

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Customer Reviews

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Rated 5/5

OXBOX Not just hype ! WOW !

I am a full time (Simi-retired, but still gigging and playing a lot) musician. Though I do have three really nice tube amps, I have been on a Kemper for a few years at least half the time , if not more, due to it just being easy and convenient. However , I still do gigs with my Tube amps and record with my real amps about half the time. Also, though I actually have a barricaded area in my 25'X25' band room studio to isolate a guitar cab for recording and it not be loud in room, I decided to give the OXBOX a try. I managed to pull up an extremely close a similar Cab sound as my Todd Sharp 2X12 ( which is similar to a VOX 2/12) and did an A/B recording test back and forth comparing My SM57 / Aston Origin Mics to the OXBOX . Other than having many more options for different cabs and mics with the OX, I just wanted to hear if was Organic and real sounding and if it would capture the true sound of my "Tube Guitar rig " . Well it certainly does ! Even if I had a better Amp room and a few more mics , I would still just use the OXBOX ! I also plugged one of my Amp heads a pedal board into it and did a few songs direct to PA with my SOLO Act set-up . WOW! It does what it does extremely well. No Buyers remorse at all on this fine piece of gear ! I highly recommend The OXBOX !
Rated 5/5

Guitar Cabinet and mic Heaven

I was hesitant to pull the trigger on the OX box as many time you hear bad reviews and misleading info on the World Wide Web. I was looking into buying another load box that's more budget friendly but decided to give the OX a try as it was highly recommended from my sales engineer Richard Whittington. This is by far one of the best purchases I've made in a while. It compliments my Soldano SLO30 and the variety of mics and cabinets is well thought of for professional recording and plying live.
Music background: Guitar Player
Rated 5/5

Best attenuator on the market! And sounded like a great recording interface!

I saw & heard this great box for 7 hours during a Lick Library bootcamp, and was impressed with the tone coming across from Sweden to me in Colorado, USA over the net.

I got tired of my Kemper and stereo FFFR cab, so I went in on a huge EVH 5150 IIS EL34 head, a 2x12 Mesa/Boogie cabinet, and a pedalboard that's still under construction :-)

Go figure that an arena amp at 100 watts is a loud home office rig. I had Jens Kruse (Kruse Amplification) install all of his mods on the EVH head, but the Variac circuit down to 5 watts just wasn't doing it for me. I still had to turn down each volume to below 1, making the amp sounded a little fizzy.

3 days ago I did a side-by-side of my Kemper EVH profiles to the real EVH amp, and the dynamics, even when fizzy in tone was just no comparison, so I ordered the OX just for the purpose of attenuation, not even for the other many great capabilities that it can offer.

I go back 40 years with attenuators to the Scholz Power Soak in 1982, and have tried Hot Plates, Power Breaks, Fryette Power Station, and more. The OX sounds *great* and there is nothing to adjust, other than volume. It really does seem dynamic, with the tone of a cranked amp *and* cranked speakers ("cone cry"). Truth in advertising with "cone cry" -- it's really there!

Not only is this a great product, but my Sales Engineer, Jimmy Hart, in a matter of minutes refunded me the approximately $50 that I noticed the OX had been reduced by in the last 3 days since I ordered it. That's service!!! Oh, and did Sweetwater ever pack this unit up like a tank to protect against any damage!
Rated 5/5

Great Box

Im coming from an Axe FX III. There was always something
missing in the tone in the Axe fx . I did come from tube amp background in the past so i got a Marshall and the OX Box and i have to say hours into setup and testing I was happy. You just cant replicate the sound, feel and connection you get with a tube amp. I used fractal for over 10 years.

The OX Box is incredible. There is a sea of tones you can coax from this box. I mean I've basically started with one 4x12
Cab with vintage 30's and have been using it since for months
The mics and cab parameters are incredible you can make some small adjustments and your getting incredible tones. the EQ in this box is so sweet. You get an eq on all mics
and on the output. Compressor is also great along with the reverb and delay.. as far as the Attenuator i don't use it.
Ive used attenuation in the past and there was alway a trade off. Little tone loss but I've never had intentions to use the OXBox attenuation...Wayne
Rated 5/5

The Ox created a

I have owned a 1982 vintage Jim Kelley F.A.C.S. 30/60, a Dumbleish amp without the Dumble insane price tag, since 2000. I have wanted to get the Ox for years but always had a better reason to spend $...

I broke down and bought my first Taylor acoustic, an 814ce Cocobolo LTD, and it came with Sweetwater Bonus Bucks.

I added a few bucks and took the chance on the Ox.

Wow, I have never understood why the Kelley has commanded the price it does... but now I know. I have a controllable tone that I cannot get even with the insane number of drive pedals I have.

"New Amp Day" after 20 years!!!
Music background: Pro Composer, Guitarist, Engineer, Producer, and Teacher

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What Do Our In-house Gear Experts Think?

Greg Titzer

After a few decades of playing countless amps in large venues and professional recording houses, I've spent a lot of time trying to figure out how to bring my full-sized guitar rig into my home studio. There are plenty of excellent load boxes on the market, and they're all great for rocking out when my wife and kids are asleep, but the OX's onboard processing makes it special. With my favorite Fender Deluxe Reverb cranked to the sweet spot (way too loud for the house) and the right blend of room ambience, reverb, and compression, I can get something better than my rig has ever sounded live.
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