Attention, budding ax gods: If you can hit the right notes, this compact rock box will make them sound like solid gold. The impeccably finished cabinet looks vintage, but it’s actually a postmodern mashup: Under the retrolicious grille cloth are two sets of power tubes from the classic age of rock — dual 6V6 amps, favored in the United States by the likes of Buddy Holly, and a pair of EL84s, secret weapon of the ’60s British Invasion. Flip a switch to alternate between them. Dual volume controls for each mode let you further color the tone for a jangling rockabilly sound or a fuzzed-out Hendrix snarl. Designed in 2004 by legendary amp auteur Fred Taccone, the JRT 9/15 has won scores of devoted converts — folks such as U2’s the Edge. It may look small (just 21 inches high and 38 pounds), but rest assured: This baby makes some glorious noise.