Pro-Ject Power Box DS3 Sources Power Supply

The Pro-Ject Power Box DS3 Sources power supply is an upgrade for Pro-Ject source models such as streamers, CD players and pre-amplifiers. It can also be used to power a turntable.

The power supply is a very important part of any audio system and can have a large effect on the sonic quality of the audio. This unit is designed to keep the main elements of a power supply separate from the unit and deliver power as cleanly as possible. It is a very low-noise PSU, with a high amount of smoothing.

This unit can be used to deliver clean power to up to six components and includes six leads.

Large toroidal transformer for a clean output

Linear power supplies, nowadays can use a toroidal transformer to step down the mains voltage. These have shielding between the primary and secondary windings. The Power Box DS3 has a larger than usual transformer, so that there is a large current reserve available. This is important as a lightly loaded unit generates less noise and hum. The output is at a low impedance and has a large amount of smoothing. As a result, the clean output improves sound staging and provides a very quiet background.

Good connectivity

Pro-Ject components need various different voltages. As a result leads are supplied with different sized connectors, to prevent confusion. Six are supplied in the box, 2 x 9V (1.3mm connector) 3 x 18V (2.5mm connector) and a 1 x 15V (2.1mm connector) – to connect a DC driven Pro- Ject Audio Systems turntable. Hi-grade cables are also available separately.

Build quality

The Power Box DS3 is has been carefully designed, and is made in Europe. The unit is only as big as it has to be to save materials. However, the casework is made out of rigid aluminium and will last a lifetime. The internal components are high-grade and will not fail for many years. The capacitors are low ESR types with a high capacity, at over 10,000 mFd.

About linear power supplies

A linear power supply uses either voltage regulator ICs or discreet transistors to provide regulation. The other type of power supply is known as switch mode and will not be discussed here. As mentioned earlier the main part of a PSU is the transformer. This is used to step down the mains voltage and to provide isolation.

Next comes the rectifier. This is usually made up of four diodes in a bridge configuration. After regulation, you have a form of “lumpy” DC voltage. This contains lots of AC ripple or hum. Along with noise from the mains. If this was used directly there would be lots of audible hum and “mush” on the audio.

The next stage involves smoothing the supply. This is done by using hi-grade capacitors to remove any ripple. The result is a fairly clean DC voltage, however, it is not regulated. An unregulated voltage changes depending on the load. For example, a high current draw will reduce the voltage. This is not good for anything the needs a constant speed, like a turntable motor. Additionally, off load. the voltage will shoot up, potentially damaging sensitive components.

Hence most power supplies are regulated. In the case of the Power Box DS3 there are three voltages needed. It is important that they are well isolated from each other as they should not interact. Regulation is achieved either by a regulator IC or separate transistors. Regulator IC’s are sophisticated devices that contain many internal components. There is usually further smoothing on the output from the ICs. Another issue is circuit board design. These have to be designed to keep the current paths short to prevent noise pickup. Overall a PSU is far more complex than you might think.