Pro-Ject Power Box RS2 AMP black

A switching power supply may be sufficient. But when an amplifier like the Amp Box RS2 is designed to reproduce micro-details and a three-dimensional soundstage, the quality of the current flowing through it matters just as much as the topology of its circuits. Pro-Ject developed the Power Box RS2 AMP as a direct companion to this amplifier, with a simple goal: to provide it with cleaner, more stable, and more generous current.

A toroidal transformer in service of the signal

At the heart of the Power Box RS2 AMP is an audio-grade toroidal transformer, shielded by a copper foil between the primary and secondary windings. This shielding acts as an isolation filter between the electrical mains and the amplifier: noise and interference from the power line are blocked before they reach the audio signal.

The filtering capacity reaches 40,000 µF, provided by low-ESR (equivalent series resistance) capacitors. A secondary rectification stage with precise regulation stabilizes the output voltages. The available current is 4 A, which represents a comfortable reserve for the brief, intense power demands generated by dynamic music.

For comparison, the previous Power Box RS Amp delivered 2 x 48 V at 2.5 A per output and powered several models (Amp Box RS, Amp Box DS, Stereo Box RS). The Power Box RS2 AMP focuses on a single device, the Amp Box RS2, with a dedicated design and updated protections.

Two switchable voltages, two usage logics

The voltage selector on the rear panel offers two operating modes: ±35 V and ±45 V.

In 35 V mode, power consumption and heat dissipation are reduced. Pro-Ject recommends this setting with 4-ohm speakers or when the Amp Box RS2 is placed in a closed cabinet where airflow is limited. The amplifier then operates within a wider thermal comfort range.

In 45 V mode, the output power of the Amp Box RS2 increases by up to 25%. The gain in dynamics and current reserve is measurable, but heat increases proportionally. Pro-Ject emphasizes the need for proper ventilation in this configuration. The Amp Box RS2 features automatic thermal protection that shuts the unit down in the event of overheating, a welcome safety net for installations where ventilation remains uncertain.

This choice between energy efficiency and maximum power did not exist on the first-generation Power Box RS Amp, whose output voltage was fixed.

Protection and gradual power-up

The Power Box RS2 AMP integrates a Soft Start system that limits inrush current at power-on. Without this device, the initial current spike can abruptly stress downstream components and, in some installations, trip the protection of the electrical circuit.

The internal components are selected for their low noise and are protected against overvoltage. The rigid aluminum chassis contributes both to shielding against electromagnetic interference and to heat dissipation.

Effect on sound reproduction

Replacing a switching power supply with a properly sized linear power supply produces effects that Pro-Ject describes along three lines: a lower noise floor, a more open soundstage, and better intelligibility of fine details. These improvements are consistent with what is usually observed when the power source gains in stability and cleanliness: the amplifier has a more constant reference voltage, which reduces modulation of the power supply by the audio signal itself.

The improvement will be noticeable provided that the rest of the chain (source, preamplifier, speakers, cabling) has a sufficient level of resolution to reveal these differences. On an entry-level system, the improvement will probably be more subtle.

Construction and integration into a system

With its dimensions of 206 x 71 x 209 mm and weight of 4.7 kg, the Power Box RS2 AMP shares the compact format of Pro-Ject’s Box Design range. Its aluminum enclosure is available in black or silver to visually match the Amp Box RS2.

The connection cable to the amplifier is included. The toroidal transformer of the Power Box RS2 AMP generates a magnetic field: as with the previous model, Pro-Ject advises against stacking the power supply and amplifier in order to prevent magnetic interference.

The unit is manufactured in Europe, like the entire RS2 range.

Technical specifications

Overview

• Type: dedicated audiophile linear power supply
• Compatibility: Pro-Ject Amp Box RS2 amplifier
• Function: replaces the original switching power supply

Power supply and electrical performance

• High-quality audio toroidal transformer with copper shielding
• Switchable output voltage: ±35 V / ±45 V
  • 35 V mode: reduced power consumption and limited heat
  • 45 V mode: maximum power and enhanced dynamics
• Output current: 4 A
• Power gain: up to +25% with the Amp Box RS2
• Mains power supply: 115 V / 230 V AC

Filtering and regulation

• Filtering capacity: 40,000 µF
• Low-ESR capacitors
• Regulation: secondary rectification with precise regulation

Protection and design

• Soft Start system against inrush current
• Low-noise components with surge protection
• Rigid aluminum anti-interference chassis

Sound quality

• Ultra-clean power supply for better sound quality
• Wider soundstage and better detail resolution
• Reduced background noise and better power supply stability
• High current reserve for more dynamic playback

Dimensions and weight

• Dimensions (W x H x D): 206 x 71 x 209 mm
• Weight: 4.7 kg

Included accessories

• Connection cable to Amp Box RS2

General information

• Available finishes: black or silver
• Manufacturing: Europe