Musical Fidelity Nu-Vista 300 power amplifier
Designed mainly for military and test-equipment applications, the Nuvistor sort of bridged the gap between tubes and transistors, but no bridge was needed: tubes proved to be the electronic equivalent of Route 66 to transistors' Interstate. But just as Route 66 has been rediscovered, so has the venerable vacuum tube. Finally, it's the Nuvistor's turn.
The only problem is, no one's making them anymore. So Musical Fidelity's Antony Michaelson, having decided to build a limited run of Nuvistor preamplifiers and amplifiers, went looking for the world's remaining stock---and ended up with thousands. Michaelson, who is also an accomplished clarinetist, wove an intriguing tale when he told me about his difficulties trying to corner the Nuvistor market (and the Nuvistor socket market as well, though that's not really part of this story).
The British company ended up building 500 Nu-Vista preamps and 500 Nu-Vista 300 amplifiers. Each preamp (all 500 have been sold) uses four tubes, so that's 2000 Nuvistors right there. Company policy is to keep a replacement set on hand for every unit sold, so that's another 2000. With four Nuvistors (two per channel) also in each amplifier's front-end circuitry, and a spare set on hand for each amp as well, that's a total of at least 8000 Nuvistors procured by Mr. Michaelson.
With the Nuvistor's life expectancy of approximately 100,000 hours, Musical Fidelity figures that, with the second set of Nuvistors in waiting, the life expectancy of the limited-edition preamp and amp should be 25 to 30 years. Is that long enough for you? It is for me. (But then, I'm an old goat.) And don't worry: Just because Michaelson has cornered the market, don't think he's going to stick you for an exorbitant amount when and if your amp needs replacements. A set of four Nuvistors costs $60.