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Universal Audio OX Amp Top Box is a analog reactive load box and guitar recording system for tube amplifiers. It offers five attenuation levels from completely silent through whisper quiet to full band volume, selectable 4, 8 and 16 ohm operation, UA Dynamic Speaker Modeling covering speaker drive, breakup and cone cry, and built-in UA EQ, compression, delay and reverb. A front panel RIG control recalls complete mic and cabinet setups.
Crank the amp all the way up without moving the neighbours.
A tube amplifier does not sound like itself until the power section is working, and the power section does not work until the amp is loud. That is the problem the OX exists to solve. The reactive load absorbs the amplifier's output while presenting the impedance a real speaker would, so the amp behaves exactly as it does at full volume with almost none of the noise leaving the room.
What comes out is not a raw DI signal. UA Dynamic Speaker Modeling reproduces speaker drive, breakup and cone cry, which are the parts of a guitar sound that come from the speaker rather than the amplifier, and then places virtual microphones and cabinets around it. The RIG control on the front panel recalls a complete setup rather than requiring each element to be dialled in.
Five attenuation levels cover the range from silent recording through whisper-quiet practice up to full band volume, so the same box handles a studio, a bedroom and a stage. Selectable 4, 8 and 16 ohm operation covers essentially any tube amp, and UA's own EQ, compression, delay and reverb are built in.
At a Glance
| Type | Analog reactive load box and recording system |
| Attenuation | 5 levels, silent to full band volume |
| Impedance | Selectable 4, 8 and 16 ohm |
| Speaker modeling | UA Dynamic Speaker Modeling: drive, breakup, cone cry |
| Effects | UA EQ, compression, delay and reverb built in |
| Presets | Front panel RIG control |
| Headphones | Front panel output |
What Is a Reactive Load Box?
A load that absorbs an amplifier's power output while presenting the same varying impedance a real speaker does. A resistive dummy load looks like a fixed resistor to the amp and sounds wrong for that reason. A reactive load lets the output transformer and power tubes behave the way they do into a speaker, which is where most of a tube amp's character comes from.
Who Is the OX For?
Anyone who owns a tube amp worth recording and cannot record it loud: home studios, apartments, and professional rooms that need a usable take at night. It also works on stage as an attenuator and as a direct feed to front of house.
Can I Practice Silently With It?
Yes. The attenuation range runs to completely silent, and there is a front panel headphone output, so a cranked amp can be played through headphones at any hour.
Will It Work With My Amp?
It offers selectable 4, 8 and 16 ohm operation, which covers essentially every tube guitar amplifier. Call 844-687-4208 with your amp's output rating and impedance and we will confirm before you order.
Connections
| Amp input | Speaker level, selectable 4, 8 and 16 ohm |
| Outputs | Line level, stereo |
| Headphones | Front panel |
| Speaker through | To a real cabinet at the selected attenuation level |
Why Universal Audio?
Universal Audio was founded in 1958 by M.T. "Bill" Putnam, the engineer who built the first recording console with integrated equalization and effects sends, and who designed the 1176 and the 610. The company was revived in 1999 by his sons and now does two things: it still hand-builds analog hardware in California, and it licenses and models the classics from Neve, API, Manley, SSL, Lexicon, Studer, Ampex and others rather than emulating them without authorization.
Frequently Asked Questions
Is this a genuine Universal Audio product?
Yes. Victory is a veteran owned dealer in Miami and units ship new in original packaging with full manufacturer support, including software registration rights.
Is this covered by warranty?
Yes. This unit carries the full Universal Audio manufacturer warranty, registered to you as the original purchaser. Call 844-687-4208 for the current term.
Does it work with any tube amp?
It offers selectable 4, 8 and 16 ohm operation, covering essentially all tube guitar amplifiers. Call 844-687-4208 with your amp's specification and we will confirm.
Can I still use a real speaker cabinet?
Yes. The OX attenuates the signal going to a real cabinet across five levels while also providing the modeled output.
How is it different from the OX Stomp?
The OX is a reactive load box that takes a tube amp's speaker output. The OX Stomp is a pedal that provides the speaker, cabinet and mic emulation without the load box, for use with amp emulators or line-level sources.
Why Buy From Victory Musical Instruments?
Victory Musical Instruments is a pro audio and musical instrument dealer in Miami, Florida. We support churches, schools, studios and working musicians across South Florida and ship nationwide. Every unit is new in the original factory packaging with full manufacturer support. Call 844-687-4208 to check lead time, request a quote, or arrange local pickup.