In May 2002, Wes Phillips of Stereophile walked into a room at a New York show expecting a "kludgy DIY project." Hervé Delétraz, an engineer from Geneva, had been writing about building his own amplifier, and Phillips, seeing no homemade amp, told him it was a shame he couldn't bring it. "But you're listening to it!" Delétraz replied. The amp on the floor was the first darTZeel. Its central idea is to leave out the big correction loop most amplifiers use, called global negative feedback, which checks the output against the input and fixes errors. Delétraz argues that such a correction always arrives after the error, so darTZeel circuits use only small local loops. The company says it aims to give listeners the emotional pull of tubes from solid-state circuits, and Jason Victor Serinus of Stereophile called the NHB-108 model two "the rare amp that manages to reveal the smallest details without sounding etched." darTZeel suits listeners who love the feel of tubes and want the detail of solid state.

The CTH-8550 integrated is the one to study first. Its name stands for Close To Heaven, and Delétraz told Rafe Arnott of pt.audio that 8550 means 85% of the quality of his separates at 50% of the price. Arnott, who prefers tubes at home, found it "beautifully voiced." If you stream, the LHC-208 integrated adds a streamer and DAC and takes single-ended inputs. For separates, pair the NHB-108 model two power amp with the NHB-18NS preamp, which Serinus found its ideal partner, especially over darTZeel's own Zeel cables. Delétraz thinks around 100 watts is the right amount of power, and he tells owners who need more volume to choose more sensitive speakers. Keep the preamp a shelf away from the amp, he advises, because the amp's glass top lets magnetic fields escape. Give a new preamp time, too. Chris Thomas of Hi-Fi+ points out that darTZeel's manual suggests 50 to 100 charge cycles before its batteries reach full running time.

Delétraz started designing electronics at 8, he told Stereophile, and darTZeel says he built his first audio amplifier at the engineering school in Geneva, where he took his electrical engineering degree in 1984. The first darTZeel took 16 years because, in his words, "it wasn't a full-time job and I needed to eat." He patented the circuit in 2000, and in November 2001 he wrote about impedance-matched connections in Stereophile before he had a company. NHB stands for Never Heard Before, and the NHB-108 was Stereophile's Amplification Component of 2005. Humor came with the design. The power button is a "Power Nose" below two yellow eyes, and on the preamp the volume knob is the Pleasure Control and the input selector is the Enjoyment Source. Red casework and gold panels have marked the range for two decades. The CTH-8550 led to the NHB-458 monoblocks, and their successor, the NHB-468, took nine years of work, darTZeel says. Michael Fremer was using a pair as his reference in 2022.