Pro-Ject Power Box S3 Phono Power Supply

Power Box S3 Phono is designed as an upgrade to provide clean power to Pro-Ject turntables and phono stages. It is an efficient and compact unit that should improve sound quality by keeping a higher quality power supply separate from the unit and removing any potential source of noise and hum. Having a remote power supply should obviate any possible source of interference. There is sophisticated DC filtration as well as low ESR capacitors. ESR stands for Effective Series Resistance. A low resistance is a mark of quality.

Please note: this unit is only designed for Pro-Ject turntables and phono stages. It will not work with other Pro-Ject Box models (pre amps, power amps etc) and we sell different power supplies for these models. If in doubt please contact us before ordering for advice matching your specific model.

Sophisticated filtration

This PSU is specifically designed to go with the large range of Pro-Ject Phono preamps and turntables. It has sophisticated DC filtration that will have a dramatic effect on sound quailty. Clean power is important for phono preamps as they use high gain, and are susceptible to noise pickup. The Power Box S3 Phono also makes cable management easier with only one box to deal with.

Power supply design

There are three essential components in any power supply. A mains transformer, a rectifier and some kind of regulation. Notably, some cheap PSU wall plugs are unregulated. As a result the output voltage can shoot up, off load. This is fine as long as they are feeding a following regulator.

Mains transformers are of two basic types toroidal and frame. Toroidal are efficient but more expensive. Frame types are used for smaller power supplies. There are also switch mode power supplies, but we will not go into them here. The transformer steps down the mains voltage to about 20V in the case of the Power Box S3 Phono.

Next follows the rectifier. This converts the AC voltage into DC. This is normally a bridge rectifier using four diodes. The DC created is “lumpy” as it has not yet been smoothed. Using this directly on a device would result in hum. After rectification capacitors are used to smooth the power supply making it suitable to be fed into a regulator. The regulator can be an IC or use discrete components such as transistors.

There are common types of 15V regulator IC’s for example. They generate heat so are usually bolted to a heatsink or the case. This type of regulator is known as linear, as opposed to switch mode. The purpose of regulation is to provide a stable voltage to the connected device. This is important for a turntable as the voltage controls the motor speed, in the case of belt-driven turntables. The output also has to be clean. Phono preamps have to amplify signals of a few millivolts, any noise on the power supply will be audible. Hence the amount of ripple has to be very low.

High quality casing

The quality aluminium case is only as big as it needs to be. It is designed and made in Europe and has a timeless design that will last a lifetime. The unit uses the best available components and design. Regulation is linear and there are low ESR capacitors for low output ripple.