Two-Rock Amplification became part of Premier Builders Guild, a collective of high-end guitar and amp brands in November of 2010, and the partnership has since freed designer Bill Krinard to build more of the tools that have facilitated some of the best blues and rock tones of the last decade. If you need proof, just listen to recent work from John Mayer, John Scofield, Eric Gales, Joe Bonamassa, and Matt Schofield.

Two-Rock’s mission has always been, in significant part, dedicated to tone transparency—making amps that capture the individual voice of a guitar down to the last detail. With the new EXO-15, the company focused on capturing that accuracy and transparency in a small, studio-friendly unit.

A Modern Tone-Aged Family
Two-Rock’s pint-sized, point-to-point-wired powerhouse is built with a lot of the same design considerations as the rest of the company’s products, though a crafty bit of redesigning went into making the EXO-15 the compact creature it is. Krinard and fellow Two-Rock designer Chad Mangrum discovered that cutting the middle of the powder-coated aluminum chassis and moving the components to the top and bottom of the head saved enough room to fit it all in a tiny enclosure that weighs in at just over 13 pounds.

As you might guess from its name, the EXO-15 has a maximum output of 15 watts. The signal begins its trip through an all-tube preamp driven by two 12AX7 tubes that feed a class AB power amp built around two 6V6 power tubes. There’s a single 5AR4 in the rectifier section. I think it’s pretty neat that Two-Rock decided to go with a tube rectifier in their mini amp, which is pretty uncommon. (These days, most low-watt amps use solid-state rectifiers.) In this regard, the EXO-15 is similar to the tube practice amps of the ’50s and ’60s, when Supro, Silvertone, Fender, and Gibson dominated the small-amp landscape.

Feature-wise, the EXO-15 is rather Spartan. A trio of EQ controls—bass, mid, and treble—grace the front panel, along with gain and volume knobs. There’s also a contour control to shift the overall frequency shape, and a passive effects loop on the back panel of the amp. The EXO-15 is a single-channel amp, so there’s no variable gain boost available. So it’s up to you to use your guitar’s controls, the amp’s tone controls, pedals, and your fingers to dramatically alter your sound once you’ve set the amp.

Luscious Tone
The EXO-15 absolutely hits the mark in terms of delivering Two-Rock’s luscious cleans and pinpoint response. For a lowwatt amp, it sounds and feels much bigger than you’d expect—serving up plenty of volume for small, intimate gigs.

I tested the EXO-15 with Two-Rock’s Standard 1x12 cabinet, loaded with a custom WGS12-65B from Warehouse Guitar Speakers. The cab was a semi-open back, which helps emphasize the powerful clean tones that are among the amp’s biggest strengths. Using a 2011 Fender American Stratocaster, I gleefully dug into the EXO- 15 with everything set at noon, save for the gain knob, which I left at around 10 o’clock. The resulting tone was powerful and full, with robust mids and round-butrich highs. There was ample low end on tap, but not in excess or in quantities that upset the amp’s excellent balance.

The lows work well to provide a foundation for the mids and highs, and the high and high-mid frequencies bloom beautifully with this low-end support. The sum of this frequency recipe carries beautifully thanks to the semi-open back design.

The EXO-15 is nothing if not versatile. Each control has an impressive range and effect on the tone, particularly the midrange knob. Most of the time, I left the treble and bass controls at or around noon, and moved the mids in and out to conjure the balance I wanted to hear. And with that bit of tone tweaking alone, I got a copious quantity of great tones—from funky rhythms to full, expansive chording to raunchy early ’70s single-note work— with minimal knob twisting.

Even more tone variation is available via amp’s contour control. It’s subtler than any of the three proper EQ controls, but as I moved the contour control down, the mids seemed to decrease and the bass took on a darker voice. Interestingly, the highs stayed intact, but the sparkle diminishes perceptibly the more I turned the control down. There’s also a shift in the guitar’s sensitivity to pick dynamics. And hitting the strings harder yielded more sting and bite in the highs, along with a tighter low end.

Two-Rock’s overdrive flavors, while not quite the source of renowned as the company’s clean sounds, are outstanding. In the case of the EXO-15, the company’s quintessential, full-bodied overdrive takes on a dirtier voice, mostly thanks to the lower wattage and rectifier. With a 2010 Gibson Les Paul Standard at the front of the signal chain, the fully cranked EXO-15 soared with super-detailed mids that evoked more than a little Texas sabor. I also got a flat-out killer low end that was tight, audible, and organic—an ideal backdrop to the overdrive’s perfectly voiced highs and mids.

Switching to a Strat again, dropping the gain down to around 11 o’clock, and cranking the volume yielded an absolutely gorgeous, velvety drive on the bridge pickup. Adding more treble gave the top end bite and sustain that prompted mental comparisons to a vintage cranked Fender Deluxe. It was a beautiful tone that made it really hard for me to put the guitar down—and indeed, a lovely reflection of the guitar’s voice.

The Verdict
For players who spend most of their time in the studio, the Two-Rock EXO-15 is a must-try, especially if they work in multiple musical genres. It’s not a metal or super heavy-rockin’ amp by any means—at least without a powerful distortion pedal in the chain—but it doesn’t try nor have to be. The EXO-15’s ability to enable the player to effortlessly dial in great jazz, blues, and classic rock tones is truly remarkable for an amp with such little wattage. The perceived volume levels might be a bit much for players who are in the market for small tube amps because of noise constraints in their apartments or houses. This head just doesn’t sound that quiet. But the EXO-15 is a spectacular performer by any other standard. And in a cluttered world of low-watt tube amps, it stands out loud and proud.

Buy if...
you prefer vintage and classic tone, but want a little extra modern kick in the voicing.

Skip if...
you need molten gain for heavier playing.

Rating...