Since the mid ’60s, electrical engineers have been trying to drive a stake into the heart of the vacuum tube, first with transistors, then with zeros and ones. Yet the tube abides, because nothing can replicate the crunch and organic feel of warm power tubes clipping and overtones moaning.

But tube saturation comes with a heavy price, namely eviction-noticing, divorce-paper-serving volume. To tame the beast, some have crossed over to the dark reign of digital modeling amps. Universal Audio, venerable maker of professional analog studio gear, believes it doesn’t have to be that way. Their OX Amp Top Box is a premium reactive-load attenuator that lets a player tap the sonic beauty of your tube amp while sparing loved ones the ear-splitting volume.

The OX plugs into the signal chain between an amp and speakers, and uses a reactive load to emulate an additional speaker load, which allows you to drive the amp at full throttle while producing bedroom-level volume (or no volume if you choose to use a set of head phones). The OX can select 4-, 8-, or 16-ohm loads to match any speaker configuration.

The result is you hear the amp in its pre-Space-Age glory, through your cabinet, in the quiet confines of your space.

If you’ve never used an attenuator or load box, this might be the first time you experience all of your amp’s combinations of preamp and power-tube settings and the way it reacts specifically to the way you play. Let’s face it, if your gig is in small clubs or basement jam rooms, you’re unlikely to drive the power tubes on a Twin Reverb and Marshall stack. In larger venues, that pesky front-of-house man is going to mic your amp and shut you down below your sweet spot.

The OX does amp attenuation very well, but what really sets it apart is its speaker/rig emulation and dynamic room/mic modeling. Plugged into a 15-watt tweed Deluxe and 85-watt Twin Reverb, the OX was amazing. Have you ever really heard your amp (not some SIM plug-in) cranking in its sweet spot in a great-sounding room? Most of us don’t have access to big spaces, expensive room-dampening treatment, or the patience (or experience) to properly set up mics. Those of us who try to record amps know all too well how it never seems to sound as good as it should – not because of the amp, but because of the room (or lack thereof).

The OX’s six-position Rig control quickly chooses from complete setups that include emulated speaker cabinets, close mics, ambient room mics, and up to four simultaneous studio effects. Built-in wi-fi allows customization of more than 100 rig and room combinations from an iPad or Mac. Remember, this is your amp, with all its idiosyncrasies, driving the emulated speaker cabinets to breakup. Just be aware that you won’t hear this coming out of your cab, though, as the modeling output is routed to a pair of balanced line outs (for a PA mixer or recording interface), digital stereo S/PDF outputs, optical Toslink, or to the headphone jack, which makes for hours of fun with your amp in amazing studio-quality settings – all without anyone in the next room even having a clue.

The OX is a beautiful marriage of tube-guitar amplification and digital modeling. It really ties the room together… and the tube abides.

This article originally appeared in VG July 2018 issue. All copyrights are by the author and Vintage Guitar magazine. Unauthorized replication or use is strictly prohibited.