Интегральные усилители — Unison Research UNICO DUE

In the UNICO DUE, the Italian firm Unison Research pairs a valve input stage with a bipolar transistor output stage. Unison Research describes the circuit as a complete redesign of the earlier Unico circuit. The power supply gained a much larger filter capacitance and a new shielded and encapsulated transformer, and the power distribution of the output stage was reworked for better use of space.

Key specs that matter

Output is 100 W RMS per channel into 8 ohm, 180 W into 4 ohm and 290 W into 2 ohm. The capacitor bank totals 80,000 uF. Frequency response is -1 dB at 12 Hz and 100 kHz, line input impedance is 47 kohm and THD is under 0.25% at 1 kHz and 10 W. Inputs comprise three RCA line inputs, a USB DAC input, a tape monitor input and an MM/MC phono input. Outputs include tape, a volume-controlled subwoofer feed and a DAC line output. The case is 43.5 cm wide, 43 cm deep and 13 cm high.

Engineering and use context

A pair of ECC83 (12AX7) valves makes up the input section, running in pure Class A. The power section uses BJT transistors in a double complementary pair, in what the maker calls a Super-Symmetric configuration with dynamic Class A bias. Volume is set by a dedicated integrated circuit holding a programmable precision resistor network, and its buffer stage runs at 0 dB gain. The software gives it a logarithmic law like the ALPS potentiometers used in older Unison Research products. The phono board sets 47 kohm and 220 pF for MM or 100 ohm and 440 pF for MC, with gain of 40 dB MM and 50 dB MC plus an extra 10 dB by internal jumpers. Its RIAA network works actively in the bass and passively in the treble, and phono THD is 0.09% at 5 mV and 1 kHz. A two-digit display shows volume from 0.0 to 9.9 and counts down the warm-up. An OSD button puts the power stages in standby while valves stay heated, while a microprocessor lowers volume gradually if excessive output is sustained. Thermal protection disables the power stage when the inside gets too hot.

Pairing

An AV mode stores one input with a fixed volume level, so a home cinema processor can drive the Unico Due as part of a surround system at the press of the remote Push button. The DAC line output stays active in standby, feeding a separate recorder or second system.

Alternatives

Within the same Unico range, Unison Research also offers the Unico Nuovo integrated, built with two ECC83 valves, a MOSFET output stage and an optional MM/MC phono board.