The Obelisk 'x2' outboard power supply (in fact, a dual-mono power amp PSU) when
added to the Obelisk 'si', ups the ante to a full 50wpc, while allowing the original
on-board power supply of the Obelisk 'si' to dedicate itself entirely to its preamp
In other words, with the addition of this single device, the Obelisk 'si' evolves
into a fully-fledged dual-mono pre/power combination.
It is a substantial technical upgrade, and consequently a large leap forward in sonic
performance: it catapults the single-box integrated Obelisk 'si' into a much higher