There are quite a few upmarket mains distribution boards available, with more or less filtering built in and so forth.
The Supra Mains Block MD06-BS/SP is quite modest on the filtering front: it has a 'Non-Intrusive Filter' which is described simply as a 'mild transient filter', plus surge protection between all three conductors.
A green LED indicates that surge protection is active.
Less background noise
Construction is based on an aluminium extrusion, with sockets (all the common international variations are available) mounted behind a Supra-coloured faceplate. Internal wiring is good thick stuff, neatly executed.
The block doesn't include a mains lead as standard, having instead an IEC inlet: we used one of Supra's 'LoRad' one metre cables – £40 including Supra's new custom IEC connector, or £20 if purchased with the MD06/SP.
Obviously that cable plays a part in determining the sonic contribution of the mains block, as do the cables leading from the block to the equipment. Even with standard commercial leads in the latter application, though, we noticed an improvement due to the MD06, with a subtle, but worthwhile lowering of general background noise – not to put too fine a point on it, the typical result of a decent, basic mains filter.
There's just a shade more detail in the sound and we were gratified to note that clicks from our usual test appliance (a dodgy switch left unrepaired for such testing!) were definitely reduced in audibility.
We'd say that a filtered distribution block like this is a sensible solution for first-step mains upgrades to mid-range systems and in that context the value is fair.