Pro-Ject Power Box RS UNI 1 WAY TT black

The Power Box RS UNI 1 WAY TT is an external linear power supply dedicated to Pro-Ject turntables operating on 15 V DC. It replaces the original power adapter with a nearly 5 kg unit, built around an oversized toroidal transformer, substantial filtering stage, and precise voltage regulation. The expected benefit: cleaner current, less interference, and a turntable motor that runs under better conditions.

Why replace the original power supply

The switching power adapters supplied with most turntables modulate voltage at high frequency. Even if this frequency lies outside the audible spectrum, insufficient filtering or shielding can allow interference to enter the audio signal. The turntable motor, powered by less stable current, may also see its speed regulation performance slightly degraded.

A linear power supply works differently. It uses a conventional transformer (here, toroidal) to step down the mains voltage, then a rectification and filtering stage to produce stable direct current. No high-frequency chopping, no rapid switching. The result is more consistent current, with less residual noise superimposed on the output voltage.

A shielded toroidal transformer at the heart of the device

The central component of the Power Box RS UNI 1 WAY TT is its toroidal transformer, oversized compared with the needs of a turntable. Pro-Ject has inserted a copper foil shield between the primary and secondary windings. This configuration acts as an isolation transformer: disturbances present on the household electrical network (HF interference, micro-outages, background noise) are attenuated before reaching the audio circuit.

The available power reserve far exceeds what a standard power adapter can provide. With a maximum output current of 3 A at 15 V DC, the transformer has a comfortable margin to absorb current demands without noticeable voltage drop. This is especially meaningful with heavy-platter turntables, whose motor must drive a greater inertial mass at startup.

Filtering and regulation: 10,000 µF of capacitance

Downstream from the transformer, the filtering stage relies on a total capacitance of 10,000 µF, provided by Low ESR capacitors (with low equivalent series resistance). This type of capacitor limits internal losses and reduces residual output noise.

Pro-Ject states ripple rejection greater than 75 dB. In practical terms, this means that the residual mains frequency (50 Hz and its harmonics) present on the output voltage is attenuated by a factor greater than 5,600. The current delivered to the turntable is therefore very close to pure direct current.

Secondary voltage regulation completes the system. It keeps the output voltage stable, including when the load varies (at motor startup or during rotational speed changes, for example).

Soft start and overvoltage protection

The Power Box RS UNI 1 WAY TT incorporates a soft-start system (Soft Start). When powered on, the filter capacitors charge gradually, which avoids a sudden inrush current on the primary winding. This mechanism protects the transformer and prevents the “pop” sometimes heard when switching on an audio device.

Overvoltage protection completes the circuit. In the event of an abnormal voltage spike on the mains, the device cuts or limits the current to protect the connected turntable.

Design and connection

The enclosure is made of brushed aluminum, available in black or silver. It adopts the compact format of Pro-Ject’s Box Design range: 201 x 72 x 195 mm. At 4.8 kg on the scale, it weighs noticeably more than an ordinary power brick, reflecting the oversized toroidal transformer inside.

On the front panel, an on/off switch with LED indicator allows the power to be cut without unplugging the mains cable. The mains input at the rear uses an IEC C15 connector (European version in 230 V / 50 Hz). The output to the turntable is via a three-pin connector. The Connect it RS – TT 15V MiniXLR – 2.1 connection cable is supplied: simply connect it between the Power Box and the turntable’s power input, then remove the original power adapter.

Compatible turntables and restrictions

The Power Box RS UNI 1 WAY TT works with all Pro-Ject turntables powered by 15 V DC. Pro-Ject recommends it primarily for heavy-platter models, whose motor benefits most from a stable, well-filtered power supply:

• Pro-Ject RPM 9 and RPM 10
• Pro-Ject Signature 10 and Signature 12
• Pro-Ject Xtension 9, Xtension 10 and Xtension 12

Other 15 V DC Pro-Ject turntables are also compatible. Several retailers mention the Classic Evo, the RPM 5 Carbon, the X2, the X8 Evolution, and the 6 Perspex SB DC as models for which adding this power supply may be justified.

One point to note: the Power Box RS UNI 1 WAY TT must not be used with the Phono Box RS phono preamplifier, whose voltage requirements are different. For the latter, Pro-Ject offers a specific power supply, the Power Box RS Phono. Nor should this “TT” model (15 V, for turntables) be confused with the standard Power Box RS UNI 1-way (20 V), which powers electronic components in the RS range such as the DAC Box RS, the CD Box RS, or the Pre Box RS.

Technical specifications

Overview

• Universal linear power supply dedicated to Pro-Ject 15 V DC turntables
• Specially designed for heavy-platter turntables
• Finish available in black or silver

Design and architecture

• Non-switching power supply for cleaner, more stable power
• Audiophile toroidal transformer with copper shielding
• Isolation transformer limiting mains interference
• Soft Start system limiting inrush current at startup
• Precise regulation of the secondary voltage

Filtering and protection

• High filtering capacity: 10,000 µF
• Low-noise Low ESR capacitors
• Overvoltage protection

Audio performance

• Improved soundstage, background silence, and level of detail
• Ripple rejection: > 75 dB

Electrical specifications

• Input voltage: AC 230 V / 50 Hz (IEC C15)
• US version: 120 V / 60 Hz
• Output voltage: 15 V DC
• Maximum current: 3 A

Dimensions and weight

• Dimensions (W x H x D): 201 x 72 x 195 mm
• Weight: 4.8 kg

Included accessories

• 3-pin connection cable
• Turntable power cable

Compatibility

• Compatible with all Pro-Ject turntables powered by 15 V DC
• Compatible with the Pro-Ject RPM, Xtension, and Signature series
• Recommended models:
  • Pro-Ject RPM 9 / 10
  • Pro-Ject Signature 10 / 12
  • Pro-Ject Xtension 9 / 10 / 12

General information

Not compatible with the Pro-Ject Phono Box RS phono preamplifier.