Rogue Audio has been building tube amps and preamps in Brodheadsville, Pennsylvania, since 1996. Mark O'Brien, the president and primary electrical designer, has an advanced degree in physics. Mark Walker, the operations manager, has a master's in mechanical engineering. They consider themselves more music lovers than audiophiles. All Rogue units are hand-built, fully tested, burned in for 24 hours, then retested. The company also employs an architectural designer, Deborah Regh, to create the Rogue Audio look: sleek and streamlined, with slightly rounded, elegant edges.

The Atlas, part of Rogue's Titan line, is a two-channel, vacuum-tube, push-pull amplifier. Its audio circuitry uses 1% metal-film resistors, ceramic tube sockets, and polypropylene coupling caps. A 12AX7 tube, configured as a paraphase inverter for the input stage, splits the signal and inverts half of it, thus creating a balanced signal pair. Those two signals are then fed into a 12AU7 triode driver stage, which boosts the signal voltage to a high enough level to drive the output stage, which uses a pair of KT77 or EL34 tubes. The Atlas comes with KT77s, each individually biased, which means that when one wears out you don't need to replace the entire quartet. They're the ones I used. Mark O'Brien says the KT77s have very nearly the midrange magic of EL34s and considerably better bass.