Michael Fremer

Not every audiophile needs an amplifier powerful enough to tax a small town's power grid while simultaneously draining his or her bank account. So, having quickly sold out of its ultra-limited-edition, extravagantly powered and priced combo of kWp preamplifier ($14,995) and kW power amp ($27,995) that I reviewed in January 2004, Musical Fidelity (footnote 1) set about capitalizing on the enthusiastic reviews earned by those giants with less expensive, less powerful, "real-world" replacements.

Nothing like scarcity to create demand, right? Well, there's been a scarcity of Nuvistors out there for decades, and hardly any demand. Do you know about the Nuvistor, aka the 6CW4? It was a tiny triode tube smaller than your average phono cartridge. Enclosing its vacuum in metal rather than glass, the Nuvistor was designed as a long-lived, highly linear device with low heat, low microphony, and low noise---all of which it needed to have any hope of competing in the brave new solid-state world emerging when RCA introduced it in the 1960s.

Nuvistors—miniature, small-signal, vacuum tubes made of metal and ceramic—were introduced by RCA in 1959, at the dawn of the transistor revolution. RCA used them throughout the 1960s in its New Vista line of television sets, mostly in the tuner section. But by the early 1970s, solid-state devices had all but replaced tubes, nuvistors included (with a few notable exceptions). Ampex based the electronics of its well-regarded, late-'60s MR-70 open-reel tape deck on nuvistors, which were also used in microphone preamplifiers—in both cases for their very low noise and reputation for reliability and long life. For a time, Conrad-Johnson used them as well. While nuvistors may seem exotic today, they're hardly rare. On eBay you can find for sale hundreds if not thousands of used and new-old stock (NOS) nuvistors, as well as nuvistor sockets, without which the tubes are less easy to implement. (But they can be, and often are, hard-wired into a circuit.)

Thoughts of power, domination, and audio road-rage enter one's mind when contemplating Musical Fidelity's SUV-like, limited-edition, 20th-anniversary offerings (footnote 1). (Only 75 sets of kWPs and kWs will be made.) The gleaming, brushed-aluminum, two-box, oversized, overweight Tri-Vista kWP preamp is fortress-like—the "kWP" looks as if chiseled into the faceplate by grimy, sweaty hands. Each of its boxes weighs almost 56 lbs. The unit's milled-aluminum remote control, the size of a Volkswagen Microbus and looking like something Fred Flintstone might wield, must weigh over 5 lbs. The kWP outputs more juice than many power amps: 55V, with 20 amps of peak-peak instantaneous current!