Усилители мощности стерео — Pro-Ject Amp Box RS2

The Amp Box RS2 is a stereo power amplifier from Pro-Ject Audio Systems in the RS2 range, built around a fully discrete class AB circuit with a tube buffer at the input. It can run as a two-channel amplifier or be bridged to work as a monoblock, and it is hand-assembled in Europe with a full metal housing finished in silver or black. Pro-Ject announced it on 30 January 2025 at GBP 1,549 or EUR 1,799.

Key specs that matter

Rated output is 2 x 80 W into 8 ohms or 2 x 130 W into 4 ohms at 1% THD, with peak figures of 100 W and 160 W per channel. Bridged, the unit delivers 280 W into 8 ohms, with a 350 W peak. Gain is 27 dB. Input impedance measures 47 kOhm on the RCA pair and 20 kOhm on the XLR pair. Frequency response covers 20 Hz to 20 kHz with a deviation under 0.2 dB, signal-to-noise is rated at 97 dBV or 100 dBV A-weighted, and the noise floor sits at -73 dBV (-76 dBV A-weighted). Channel separation is -58 dB at 10 kHz into 4 ohms, and THD stays below 0.08% at 20 W into 4 ohms.

Engineering and use context

Power comes from an external supply delivering plus and minus 40 V at 5 A DC, and it works on 100 to 240 V mains at 50 or 60 Hz, so the same unit suits different regions. Standby draw is below 0.5 W. The input stage is a differential circuit with a 6922 (6DJ8) double triode, followed by a driver stage with 2SA1552T and 2SC4027T transistors, and each output uses a pair of STD03N and STD03P devices working in class AB. Built-in thermal protection switches the amplifier off automatically if it overheats. The metal enclosure is meant to shield the circuit from vibration and interference. Its footprint is 206 x 85 x 200 mm, growing to 227 mm in depth with sockets, and the amplifier alone weighs 2660 g. Gold-plated speaker terminals accept 4 mm bananas, spade lugs or unterminated cable, and an RS232 port allows integration with external control systems.

Pairing

Since XLR as well as RCA connections are present, the Amp Box RS2 connects directly to the pre-outs of the Pre Box RS2 Digital, which shares the width of the RS2 series. The optional Power Box RS2 Amp is a linear supply with a large toroidal transformer, priced at GBP 899 or EUR 999, switchable between 35 V for lower heat and 45 V for up to 25% more output power. A second Amp Box RS2 can be added later, with both units bridged to give one mono amplifier per channel.

Alternatives

Within Pro-Ject's Box Design stereo power amplifiers, the Amp Box DS2 is the step below the RS2 in the same compact format.