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Commentator: Michele Surdi
Source: Nagra CDC, 2011Macbook Air, PureMusic 1.8, HRT Streamer 2
Amps: Nagra VPA, Nagra 300p, FirstWatt F5
Speakers: Tannoy Yorkminster, Harbeth P3 ESR
Cables: Van den Hul Inspiration biwire, The First, The Second balanced
Power: Cablerie d’Eupen, Black Magic 4
Stands: Guizu SRW2A, Music Tools One
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Last man standing. Shootouts are good clean fun. If they are to be of any use to prospective buyers—and all audiophiles no matter how straitened their circumstances answer to this description—they must follow one basic rule. No sense in comparing components built on opposing design philosophies or placed at wildly different price points. [I'd beg to differ entirely. Michele's FirstWatt F5 transistor amp would make a most excellent comparator on bandwidth, distortion and value - i.e. what do the far costlier valve amps offer which it doesn't; and where might the solid-state amp actually show its valve brethren a clean set of heels. - Ed.]
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That said, a match between my reference Nagra VPAs and Nagra’s new and newly acquired 300p amp seemed mandatory particularly since they would be evaluated in an all Nagra rig with speakers particularly attuned—good word placement there—to their strong points. This is hardly a coincidence. Both my 6-year old Tannoy Yorkminsters and latest model Harbeth P3 shoeboxes were bought specifically because of their phase-impedance characteristics. Those result in a maximum current draw of just above 4Ω resistive in the Tannoys and a tranquilizing 5Ω equivalent for the teeny Harbeths.
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Notice that no consideration was taken of the abyss between the Yorkminsters’ generous 94dB sensitivity and the P3’s glacial 83dB. This because what really matters is that the VPAs’ internal impedance is somewhat above 2Ω, not bad for a feedback-less DHT application but unconscionably high for the ampere vampires in current (pun here too) fashion. Yes I know. The VPA literature seductively mentions Wilsons and Quads. But marketing requirements and Ohm’s law never shall meet.
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There really is no reason to match speakers of 1 or 2Ω dips with DHTs. Beam tetrodes and well-applied feedback were invented precisely for this reason. I have no exact figure on the 300p’s internal impedance but it should be in the same ballpark as the VPAs’ given the similarities in output devices if not overall circuit topology.
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