Усилители мощности стерео — Concert Fidelity DHP-300B

The DHP-300B is an all-valve power amplifier from Concert Fidelity, placed in the Resolution Series and in the Royal Purple Collection of the Japanese maker. Its name refers to the directly heated 300B triode, used here in a push-pull output stage. Concert Fidelity was started in 1987 by Masataka Tsuda, who has more than 45 years of experience with valve and transistor amplifier design. According to the company, he built his first valve amplifiers at the age of 10, obtained a ham radio licence at 14 and then spent 12 years at his father's precision machining and tooling company, followed by six years at a semiconductor trading firm and three at a trader in precision measuring instruments. The maker publishes no price and asks buyers to enquire.

Key specs that matter

A pair of WEC 300B type output triodes delivers 20 W into 8 ohm. They are driven by one 6SN7 double triode, and rectification is handled by a 5AR4 or GZ34, with a WE-274A type rectifier available as an option. The line input is single-ended RCA with an impedance of 100 kohm, and the speaker terminals offer 4 ohm and 8 ohm taps. The chassis measures 450 x 140 x 260 mm and weighs 18 kg. Valves are not included in the delivery.

Engineering and use context

Between the 6SN7 and the output valves sits a custom interstage transformer, so the driver couples to the 300B grids magnetically rather than through capacitors. Every transformer in the amplifier is made to order in Japan. Versions are offered for 100, 110 to 120, 220 to 230 and 240 V mains, each fitted with a power transformer for the market it is sold in, and repairs are guaranteed only within that market. Since the buyer sources the tubes, the choice of 300B brand and of the rectifier type, including the optional WE-274A, is left open.

Pairing

With its modest output and a single RCA input, the DHP-300B calls for efficient loudspeakers and a preamplifier with a single-ended output. The matching unit in the same Resolution Series is the CLS-050 Mk2 line stage, which uses a pair of 6V6 valves with a custom output transformer, adds 6 dB of gain and provides one balanced and two single-ended outputs. The speaker taps let the output transformer be set to the nominal impedance of the loudspeaker in use.

Alternatives

The Concert Fidelity DHS-300B is the single-ended 300B amplifier of the same series, rated at 9 W per channel with 6SJ7 driver valves.