Предусилители — Accustic Arts TUBE PREAMP V

The TUBE PREAMP V is the tube hybrid version of the reference preamplifier line from Accustic Arts, handmade in Germany. It is a fully balanced line-level design that places four reference tubes, two per channel, into an otherwise solid-state circuit. The company develops it separately from the transistor PREAMP V rather than deriving one from the other, so neither can be converted into the other, yet the two sell at practically the same price and accept the same phono upgrade.

Key specs that matter

There are three balanced XLR inputs, two unbalanced RCA inputs and a sixth RCA input usable as a surround bypass. Main line outputs are duplicated in both XLR and RCA form, joined by a fixed-level RCA output, an unbalanced XLR output, a 6.3 mm headphone socket and two switchable unregulated feeds for an outboard headphone amplifier. Frequency response spans DC to 50 kHz within +0 and -0.5 dB and DC to 120 kHz within +0 and -1.5 dB. Noise is quoted at 95 dB unweighted and 103 dB A-weighted, total distortion plus noise stays under 0.0015 percent, crosstalk is better than 99 dB and maximum output is 18 V. Input impedance is 2 x 50 kohm balanced and 50 kohm unbalanced, with output impedance of 2 x 50 ohm and 50 ohm respectively.

Engineering and use context

The tubes can be replaced without any adjustment - Accustic Arts calls it plug and play. After them comes a high-end Class A output stage built around Burr Brown OPA 627 op-amps, and inputs are switched by relays with gold-plated contacts. Power is drawn from two magnetically shielded 50 VA toroidal transformers made in Germany. A digital volume control working on four channels keeps crosstalk low and holds channel balance within 0.2 dB from 0 to -60 dB. Of each output pair, one is AC-coupled through 3.3 microfarads and the other is DC-coupled. A phase switch flips polarity between 0 and 180 degrees, and a high-resolution colour display shows the settings. Consumption is about 20 W in operation and under 0.5 W on standby. The aluminium case with chromed brass knobs measures 128 x 482 x 393 mm and weighs 16 kg.

Pairing

With its high output voltage and low source impedance, the unit can drive long balanced runs to one or two power amplifiers, and the AC-coupled outputs protect amplifiers that should not see very low frequencies. Owners who later add a turntable can have the MM/MC phono board fitted instead of buying a separate stage.

Alternatives

The Accustic Arts PREAMP V is the all-transistor line preamplifier developed in parallel with this tube hybrid model.