The Amp Box RS2 is a stereo power amplifier in class AB, built from discrete parts and fronted by a valve input stage: it delivers 2 x 80 W into 8 ohm and 2 x 130 W into 4 ohm and can be bridged to work as a mono amplifier.
Amp Box RS2: power and connections
The power circuit is discrete throughout and runs in class AB, a choice that pairs low distortion with good efficiency. As on other RS components, the incoming signal goes through a valve buffer before it reaches the output stage. The case is all metal and is not there for looks alone: it helps shed heat and shields the circuits from vibration and interference.
In stereo, continuous output is 130 W per channel into 4 ohm and 80 W into 8 ohm, measured at 1% distortion, with peaks of 160 and 100 W. Bridged, the unit becomes a mono amplifier giving 280 W continuous into 8 ohm, with 350 W on peaks. There are two line inputs, one RCA and one balanced XLR; the gold-plated speaker posts take spade lugs, bare wire or 4 mm banana plugs, and a three-pin terminal block carries RS232 control.
Power is external: an adaptor rated at ±40 V and 5 A comes in the box. Those who want more can swap it for the Power Box RS2 Amp, sold separately, a linear supply whose large toroidal transformer is screened between primary and secondary to keep mains noise out and which, according to Pro-Ject, yields up to 25% more output.
Specifications
- Operating class: AB, discrete circuit throughout
- Continuous power, stereo: 2 x 130 W into 4 ohm, 2 x 80 W into 8 ohm (1% THD)
- Continuous power, bridged: 280 W into 8 ohm (1% THD)
- Power on peaks: 2 x 160 W into 4 ohm, 2 x 100 W into 8 ohm, 350 W bridged into 8 ohm
- Noise floor: -73 dBV, -76 dBV A-weighted
- Frequency response: 20 Hz to 20 kHz inside -0.2 dB
- Channel separation: -58 dB at 10 kHz, 4 ohm load
- Signal-to-noise ratio: 97 dBV, 100 dBV A-weighted
- Harmonic distortion: below 0.08% at 20 W into 4 ohm
- Gain: 27 dB
- Input impedance: 47 kohm on RCA, 20 kohm on XLR
- Line inputs: 1 stereo RCA and 1 stereo XLR
- Speaker posts: gold plated, for 4 mm bananas, spades or bare wire
- RS232 control: plug-in terminal block, 3 pins
- Power: external ±40 V / 5 A DC unit, 100-240 V mains
- Standby draw: under 0.5 W
- Size: 206 mm wide, 85 mm high, 200 mm deep (227 mm including sockets)
- Weight: 2.66 kg, power supply excluded
- Finishes: black, silver
