Dennis Had built his first amplifier as a seventh-grade science project, and it won a blue ribbon. His father's string quartet practiced in the family home every Friday night, and Had spent years trying to make the quartet's records sound like the real thing in the room. Many tube amplifiers split the music between two output tubes and join the halves again at the end. A single-ended amplifier, the kind Cary is known for, passes the whole signal through one tube, and the CAD-300SEI does it with a single 300B. The trade is power, so it needs speakers that are easy to drive. Robert Harley of Stereophile came to the 300SEI biased against single-ended amps and left convinced that they "sound fabulous in spite of their distortion, not because of it." Art Dudley heard "an uncanny ability to pull solo voices forward." Cary suits listeners who care most about voices and tone.

Start with the speakers. The 300SEI makes about 11 watts a channel, and Harley paired it with Infinity speakers of high sensitivity. If your speakers are harder to drive, the SLI-80HS integrated uses four tubes in push-pull and has a switch for Triode or Ultra-linear operation. Edgar Kramer of SoundStage! Australia suggests Ultra-linear, the more powerful setting, for speakers of moderate efficiency or low impedance, and Triode for a sweeter, richer sound. Ken Micallef of Stereophile heard the SLI-80HS throw a layered soundstage that "sounded practically 3D." Steve Huff ranks the bigger SLI-100 among the best amps he has heard with Klipsch Heritage speakers. The SLP-98 preamp has been in production since 1998, and Steve Guttenberg hears it "right in the middle" between tube and solid-state sound. For the most power, the solid-state SI-300.2D makes 300 watts a channel, and Pursuit Perfect System heard warm bass it called "bouncy or rounded."

Had grew up with ham radio and held a license at 11. As a teenager he saved his paper-route money for a 300B while his friends bought 6L6s, and he still had that tube when Stereophile interviewed him in 1995. He founded two RF companies and sold the second in 1983, then walked into a new high-end store in Cary, North Carolina, and was surprised to find brand-new tube amplifiers for sale. The owner asked him to repair some, and Had decided he could build better ones. He and his wife Donna founded Cary Audio Design in 1989 and named it for the town, and new Cary gear is built in nearby Raleigh. Ken Micallef writes that Conrad-Johnson and Audio Research repopularized tubes in the US in the 1980s and that Cary "brought SET designs to the mainstream in the early '90s." Art Dudley credits Had with making "SETs that were safe for the world," with a load switch, a balance control and a headphone jack.