Усилители мощности моно — Concert Fidelity ZL-120FX2

The ZL-120FX2 is a transistor monoblock power amplifier listed by Concert Fidelity in its Reference Series. The Japanese firm was founded in 1987 by Masataka Tsuda, who remains the sole designer, with production handled at its own Nagano workshop. The model descends from the ZL-120 and the later ZL-120FX, and in the current catalogue it sits beside the ZL-200FX2 monoblock and the ZF-100FX stereo amplifier. The maker publishes no price and refers buyers to its distributors, while a pair of the preceding ZL-120FX carried an MSRP of USD 30,000.

Key specs that matter

Each monoblock delivers 180 W into 8 ohm. The input is RCA only, with an impedance of 47 kohm and a sensitivity of 2 V for rated power, and voltage gain is 20 dB. Concert Fidelity quotes a frequency response of 0.5 Hz to 30 kHz with no deviation and 0.5 Hz to 100 kHz at -0.8 dB, both measured at 0.125 W. Power consumption in operation is 140 W at 120 V AC. Each chassis measures 450 x 150 x 360 mm and weighs about 20 kg. Units are built for 100, 110 to 120, 220 to 230 or 240 V mains, and the mains transformer is wound for the country of sale, outside of which warranty cover lapses.

Engineering and use context

Tsuda aimed for the simplest possible circuit with as few components as he could manage, so each monoblock uses just two pairs of MOSFET output devices, arranged in BTL configuration and run without overall negative feedback. The FX revision added Japanese-made DC-DC converters to the input and driver stages. Unlike linear regulators, these converters isolate the stages from one another electrically, which the maker credits with a lower noise floor. The driver circuit board was revised to the LF-4 V2.0FX version and the grounding layout was reworked at the same time. The amplifier also borrows the power supply section of the larger ZL-200, so it can supply noticeably more current on demand, and Concert Fidelity names the ability to drive less efficient loudspeakers as one result.

Pairing

Because there are no balanced inputs, the preamplifier has to provide a single-ended RCA output, and it needs enough output voltage to take the monoblocks to full power. The in-house partner is the CF-080LSX4 hybrid line stage, which has four RCA inputs, one of them switchable to XLR, a 100 kohm input impedance and gain selectable between 6 and 12 dB from two 12AU7 valves in cascode. Given that output from each chassis, loudspeakers of modest sensitivity are within reach, in line with the extra current the ZL-200 power supply provides.

Alternatives

The Concert Fidelity ZL-200FX2 is the other monoblock of the brand, rated for the same power but using four pairs of output MOSFETs.