IsoTek certainly didn't invent the mains conditioner (people were selling them before the company started trading), but it has certainly made a big mark in aftermarket mains kit.

This must be partly due to the sheer range of products available; at the time of writing, the company's website lists over a dozen models at a variety of prices.

But there are plenty more in the pipeline, including the latest model Sirius, which is part of the new 'EVO3' range.

Well-built kit

Set to replace the GII products, Sirius is a simple enough proposition, a six-way distribution board, good for ten amp output (2,300-watt) with filtering and protection built-in.

Unlike the PS Audio Quintet, it doesn't include any switching features, but then it is considerably cheaper. It does, however, come with handy wall-mounting brackets.

£250 might still seem a lot of money to throw at a 'mere' mains accessory. But it's an expense that can easily be justified in the build quality of the Sirius, which is very high. The basic chassis is a substantial piece of aluminium extrusion, on which are mounted high-grade sockets.

The mains inlet is a standard IEC type, which IsoTek naturally recommends should be fed via one of the company's own mains leads. The clever stuff is inside, on a modest-looking circuit board which carries all the filtering components.

Effective isolation

Arguments rage in the nerdier corners of hi-fi-dom about how best to filter mains supplies. The Sirius adopts a relatively non-intrusive approach, with mostly shunt-connected components that are not 'in the way' of the mains voltage.

There are also protection devices capable, apparently, of handling 22,500 amps, a claim we're happy to take on trust in the absence of a sudden lightning strike to use for testing.

Rather ingeniously, IsoTek has also come up with a simple, but effective means to provide a degree of isolation from socket to socket, so that mains noise generated by one component does not significantly affect other components plugged into the same board.

This is not always taken into account - certainly not in any of the cheaper mains boards we've seen.

Improved sound quality

It is only honest to add to any review of a mains filter or conditioner that your mileage may vary.