Усилители мощности стерео — Ayre Acoustics VX-5 Twenty

The VX-5 Twenty is the stereo power amplifier of Ayre Acoustics' 5 Series, designed and hand-built in Boulder, Colorado. The Twenty designation marks an upgrade package that Ayre applies to existing 5 Series products rather than replacing them, and earlier VX-5 units can be brought up to the same specification at the factory.

Key specs that matter

Output is 175 W per channel into 8 ohms and 350 W into 4 ohms, continuous. Gain is 26 dB and frequency response extends from DC to 250 kHz. Input impedance is 1 Mohm unbalanced and 2 Mohm balanced (1 Mohm per phase). Inputs are one XLR and one RCA pair, and outputs are two pairs of binding posts. Power consumption is 35 W in low-current mode and 325 W in operating mode without signal. The chassis measures 440 x 480 x 120 mm and weighs 24 kg.

Engineering and use context

Ayre uses discrete parts throughout, a balanced topology with zero global feedback. The output stage uses Ayre's Diamond topology, in which pairs of bipolar transistors are connected via their emitters and bases as an alternative to a conventional push-pull arrangement. The Twenty version adds a further buffer stage based on the same diamond principle, a double diamond configuration that raises efficiency and lowers heat output, by about 35% according to Ayre. The diamond buffer principle goes back to work by Richard Baker in the 1950s, long before suitable complementary transistors existed. Ayre's Equilock circuit holds the operating conditions of the gain transistors constant regardless of signal, reducing a source of distortion. The power supply is linear. Circuit boards use high-speed material, resistors are custom audio-grade parts developed for Ayre, and the Ayre Conditioner filters radio frequency interference from the mains. AyreLink communication lets Ayre components switch on and off together. Because gain stages are balanced throughout, a single-ended source is converted internally. Two pairs of binding posts allow bi-wiring, and the 5 Series philosophy of periodic upgrades means the amplifier can be returned to Ayre for future revisions.

Pairing

Because its output doubles into 4 ohms, the VX-5 Twenty drives low-impedance and low-sensitivity speakers. Its very high input impedance presents virtually no load to valve or solid-state preamplifiers, including Ayre's KX-5 Twenty.

Alternatives

Ayre's MX-R Twenty is the mono power amplifier of the brand using the same Twenty upgrades in a separate chassis per channel.