Universal Audio OX Amp Top Box

Editors' Pick - Article from Guitar Player Magazine - June 2018

Tested by Art Thompson

Amplifier attenuators have been around for decades, and modern, reactive-load devices have become standard items for players at the full bore but need to reduce the wattage that hits the speakers to keep the volume in check.

True to form, Universal Audio’s OX Amp Top Box is designed to let you run your tube amp (up to 150 watts) at its optimal volume setting, while letting you control the output to the speakers with a 6-position Volume switch. However, good as it is at preserving the tone and the feel of an amp while significantly lowering the volume, OX is afar more than a mere reactive load box. It also routes some of the attenuated signal into a digital section that – when the software app for Mac or iPad is enabled – provides 100 “Rigs” (i.e. preset combinations of various speakers, mics, and effects), that can be modified to create your own custom rigs by selecting from a menu that includes 17 speaker cabinets, eight close mics and six room mics, as well as studio-grade compression, delay, EQ, and plate reverb.

Note that the “modeled” sounds are only available from OX’s dual ¼” balanced line-outs, S/PDIF digital outs (RCA and optical TOSLINK), and headphone out. On other words, they do not affect the attenuated signal that’s feeding a standard speaker cabinet.

OX’s front-panel controls also include spate Volumes for the line and headphone outs, a six-position Rig selector (which is user configurable via the software app), and a Room knob that varies the amount of “studio room ambience” – turn it up for an airier sound, down for a drier response. Room only affects the line, digital, or phone outs, and its settings can also be edited and stored via the app.

You can use OX without a computer, of course, but the app is necessary if you want to deep dive into all of the pre-configured Rigs and/or edit those presets to create and save your own custom Rigs. And since the app is such a big part of the user interface, UA thoughtfully equipped OX with its own built-in Wi-Fi network, which – once the app is downloaded onto your Mac or iPad and a password established – provides reliable communication between OX and your chosen device, regardless of internet availability. The only problem I had was that OX stopped passing signal twice during these tests and had to be switched off and on again to restore operation. The app was not running at either time, so the cause didn’t seem to be Wi-Fi related.

The hardware side of OX is brilliantly executed. The unit features a heavy-gauge aluminium housing with plenty of vent openings, and the front panel looks retro with its two-tone color scheme, large knobs, wood trim, and jeweled indicator lamp. The in-line 12V DC power supply connects to main unit via locking XLR jack, and extra-tall rubber feet provide plenty of clearance for the amp’s handle when placing OX on top of a head or combo. Nice! There’s a foot switch jack on the rear of the panel that the manual describes as “not functional.” However, by plugging in a momentary footswitch (not included) OX turns into a looper of sorts: It records, plays, and stops, but won’t store anything. Heck, I wouldn’t mind if it just let you toggle the Rig selector via footswitch.

Even before I started controlling OX with the app, it was fun to hear my amps through the six “factory” selections of miked 4x12, 2x12, 1x12, and 4x10cabinets available on the Rig dial. The really cool thing is that my vintage Marshalls (’66 JTM 50, ’69 PA 20, and ’72 JMP 50), as well as a Fender Deluxe Reverb, Mesa Mark 5:25, Sound City SC30, and Vox AC10 all maintained their distinct sonic and dynamic signatures when driving into OX at all sorts of different volume and gain settings. It’s literally like taking your amplifier collection into a great-sounding room (which can sound two different ways by using the DAMP function), with aqesome mics and hearing them as perhaps you never have. Of course, the app lets you switch speaker cabinets, use different mics and adjust their positions, layer on superb sounding effects, and save these custom sounds in the app and/or to the Rig selector for live or recording situations where you don’t want to be toting a computer or tablet. Pack your fave amps and OX Top Box, and now you’ve got studio-quality tones at your fingertips with zero hassle. And since all of the outputs are available simultaneously, OX can readily be implemented into a live sound setup, where you’d run your amp through standard cabinets onstage, send a direct feed from the line-outs to a monitor system or the FOH mixer, and maybe use the digital outs to feed a DAW or other device. If you’ve ever lusted for a 3D soundstage when playing larger rooms, OX can certainly help get you there. OX is brilliantly engineered device with so many applications possibilities, but even if you simply use it to enjoy your tube amps in astonishingly realistic studio environments, there’s a mighty good case for owning one. ‘Nuff said, I love it!

Kudos Amazing speaker cabinet, microphone, and studio room simulations. Really good load box.

Concerns Required reboots on a couple of occasions.