Усилители для наушников — Auris Audio Ultima KT88

The Ultima KT88, which Auris Audio sells under the shorter name Ultima 88, is a valve headphone amplifier with a built-in line preamplifier from the Serbian maker. Auris presents it as the younger sibling of the Headonia 300B and builds it in the same style of milled aluminium case, but where the Headonia relies on directly heated triodes, the Ultima puts two KT88 beam tetrodes in its output stage. They are preceded by two 6SN7 double triodes, a type also sold as CV181. The launch price was USD 11,099, and the maker's own online store later listed it at EUR 9,900 with a delivery time of four weeks.

Key specs that matter

Rated output is 8.6 W, and Auris states that this maximum stays the same at every position of the five-step impedance switch - 32, 80, 150, 300 and 600 ohm. The voltage available at the output rises from 16.6 V on the 32 ohm tap to 26.2 V at 80 ohm, 36 V at 150 ohm and 51 V at 300 ohm. In high gain the THD+N figure is 2 percent at 1 W and 0.5 percent at full output, while a low gain mode capped at 100 mW reaches 5.8 percent at its own maximum. Frequency response holds within 0.35 dB and noise sits more than 90 dB below full output. Full output needs 2 V on the single-ended inputs or 4 V on the balanced one. The case is 440 x 480 x 240 mm and the unit weighs 19 kg.

Engineering and use context

Auris winds the output transformers by hand in its own workshop, using copper wire sourced in Serbia, and the impedance selector chooses between their secondary taps so that the KT88 stage works into a load close to the one it was designed for. Balanced sources pass through Lundahl input transformers before reaching the valves. Level is set with a Japanese Alps potentiometer, and the signal path uses capacitors made by the German firm Mundorf. According to Auris, the milled aluminium enclosure is there to limit mechanical vibration and electrical interference around the circuit.

Pairing

For sources there are two RCA stereo inputs plus a single XLR socket, while headphones plug into a 6.3 mm jack or a 4-pin XLR socket. Because power does not fall off on any tap, low-impedance headphones can use the lowest setting and high-impedance models the two highest settings. The preamplifier section has both RCA and XLR outputs and gives up to 2.5 V from a standard line-level input, with 0.02 percent THD+N, response within 0.3 dB and more than 90 dB of signal-to-noise, which lets the Ultima run a separate power amp or active monitors as well.

Alternatives

The Auris Audio Lyre is the compact valve headphone amplifier of the brand, rated at 1 W into 32 ohm in an 8 kg chassis.