Pre/Power Amplifiers

This second-generation series of Progression amplifiers benefits from more than a little trickledown from the brand's quarter-tonne Relentless monoblocks [HFN Mar '20]. The high voltage 'Super Rail' input/driver stage stems from that flagship but, more importantly, so does the switch from Sanken to matched pairs of OnSemi bipolar output transistors. Both the S350 reviewed here and the partnering M550 monoblocks are built onto the same 'machined from a 22kg block' alloy heatsinks and host the same 2kVA Keen Ocean transformer feeding no fewer than 12 pairs of OnSemi power transistors per side. For the S350 each balanced 'side' is either the left or right channel while in the M550 one is a 'negative-going' and the other a 'positive-going' side of a bridged pair. Achieving very high power outputs into a moderate 8 or 4ohm – the M550 is rated at 550W/8ohm – is as much about delivering a high voltage across the load (>65V for ~550W/8ohm) as supplying the current to support it, which is why D'Agostino, along with Musical Fidelity, Hegel and others, opts for a balanced/bridged-mode configuration in its highest-power amplifiers. PM