Electric guitarists can spend years searching for tube-powered amplifiers that will give them the perfect tone.

Now many of them are on the hunt for the tubes themselves.

Long made obsolete in most consumer electronics by printed circuit boards, vacuum tubes are still used in guitar amps and hi-fi equipment. Aficionados say the tubes—just a few inches tall, with heated filaments that resemble a dimly glowing bulb—provide a warm, creamy tone unmatched by solid-state circuitry. 

“It’s something I don’t think you can actually put into words,” said Peter Frampton,  whose bestselling 1976 album “Frampton Comes Alive!” was a showcase for tube-amp-powered guitar solos. “Whatever you put through an amp with tubes is going to have extra warmth.”