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Clips recorded with Gibson ES-335 Historic, Planet Waves Custom Pro Cables, Shure SM57, and Apogee Duet into GarageBand.
While many collectors acquire guitars and amplifiers, Tony Bruno is constantly on the search for capacitors and resistors, both new-old-stock (NOS) and modern. Bruno keeps a library of these parts in the upstate New York shop where they become the guts of some of the most coveted boutique tube amps in the world today. Some of these amps—like the Underground 30, a mid-powered machine, and the Cow Tipper Pro II 22, a 22-watt, 6V6 blackface Fender-inspired model— have already become legend. Bruno’s reputation even led to a gig working with Vox on the design of new amps.

Bruno’s latest offering under his own name is the Underground Custom, an evolution of the Underground 30 that incorporates different capacitors and resistors, adds a Mid control, and includes a negative feedback loop that re-voices the amp significantly. The amp is the product of Bruno’s restless need to refine his work, and that drive has won over more than a few high-profile guitarists. One of Bruno’s most prominent fans is country superstar Brad Paisley, who set aside his beloved Trainwreck in favor of a new Underground for recording the leads on his forthcoming album,This is Country Music. Given this endorsement and Bruno’s work to date, we were super-psyched to review the amp.

Gorgeous and Stone Solid
The Underground Custom is one handsome amp. Our review model arrived clad in black vinyl (though the amp can be ordered in a variety of coverings), which contrasts nicely with its silver grille and white vintage-style chicken-head knobs. The Bruno also manages to combine Fender, Vox, and old Marshall styling cues without looking derivative. On the grille you’ll find an especially tasteful flourish, a simple Bruno logo in an art deco–style font that underscores the amp’s vintage aura and classy, upmarket feel.

Bruno spared little expense in building the impressively solid Underground Custom. The head’s chassis is made from heavy-duty steel and the cabinet is constructed from finger-jointed solid pine and 13-ply Baltic birch baffles, which discourage rattling and unwanted vibration. Both the head and cabinet have thick, padded handles for comfortable hauling.

Inside the Underground Custom, the handwired, point-to-point circuitry incorporates CTS pots and other high-end electronics. The tube sockets are made of ceramic, and everything is held together with stainless-steel screws and bolts.

The non-master-volume Underground Custom has a somewhat unconventional tube configuration—five EL84s and four 12AX7s. However, that extra EL84 isn’t for power, it’s a reverb driver. Like the Underground 30, the Custom features about 36 watts of class-A power. But unlike its predecessor, the Custom has a solid-state rectifier in place of a GZ34.

The Custom’s front panel is elegant and simple. At the far left is a single 1/4" input, followed by three controls for the built-in reverb—Mix, Tone, and Dwell—that will be familiar to anyone who has used a standalone Fender Reverb unit. To the right of the reverb controls are the amp’s Treble, Mid, Bass, and Presence knobs, followed by a pilot light and the standard standby and on-off toggle switches, plus a ground switch. On the back of the amp are 1/4" outs for 8Ω and 16Ω speaker configurations.

Positively Killer Sounds
I auditioned the Underground Custom head with a half-open Bruno cab equipped with two 12" Celestion G12-65 speakers. Plugging a recent Gibson 1963 ES-335 Historic with factory Burstbuckers directly into the Custom, I was blown away by the amp’s power. Set on 2, it seemed as loud as other 30-watt models do at much higher volume settings.

Bruno says he conceived and voiced the Custom for lead playing. So I first tried some single-note lines in a variety of idioms, including blues-rock and modal jazz. The Custom did indeed impress in all these contexts, delivering a warm and spongy sound filled with blooming harmonics and uncommon definition and sustain.