Musical Fidelity Nu-Vista 300 power amplifier Page 2
Despite its high profile in the Nu-Vista 300's very name, the Nuvistor tube is not the 300's main amplifying device. How many of the little guys do you think it would take to output 300Wpc into 8 ohms---or 600 into 4, or 1000 into 2? Instead, the Nuvistors are used as drivers for what the literature describes as "ultra-low-noise, super-matched pairs of bipolar [output] transistors."
If your familiarity with Musical Fidelity products begins and ends with the "good for the money" budget-priced X series, leave your preconceptions at the speaker terminals---this is a very serious product. And though at $5495 it ain't cheap, given what you get physically, sonically, and in terms of sheer, raw power, it's a bargain.
With its curved diecast sides and a gleaming fascia fine-machined from aluminum mil-spec billet with polished-brass vertical accents, the long but compact two-chassis design looks and feels as weighty as it ended up sounding. But while the two boxes look similar, the Nu-Vista 300 is not a monoblock: one chassis houses the power supply, the other both channels of amplification.
While the conventional wisdom is that monoblocks offer physical and sonic advantages in high-power designs, Musical Fidelity's position is that the high current and voltage swings produced by large amplifier power supplies can create magnetic flux, which can then interact with the circuitry, interconnect cables, components, or even the amplifier case, and thus degrade the sound. Monoblocks can also have different ground potentials, which can affect imaging. So MF puts two mono amplifiers in one box and both power supplies in the other.
The choke-regulated power supply includes three transformers: one for each channel, and one for the control circuitry. Rather than the quick pulses of charging current featured by a typical diode-bridge/reservoir-capacitor power supply, which can generate RF spuriae, the choke topology provides a more continuous source of charging current to the storage caps. While Musical Fidelity claims to be the only manufacturer using this particular three-transformer approach, Ayre uses something similar in its V-1 (reviewed in the September 1999 Stereophile).
Five LEDs are sunk smartly into the aluminum surface of each fascia. Push the Power button centered on the front of the power supply, and the amp begins a run-in sequence of lights that first blink orange, then green. When the four on the power-supply side and the center one on the amp side turn green, the amp is ready.
With its custom-made, die-cast, 15.5kg rounded heatsinks and its long, low-slung double chassis, the Nu-Vista 300 reminds me of a pair of large-gauge model train cars. Before you even listen to any music, the amplifier exudes power and authority. It screams "expensive."
Two cables fitted with locking Neutrik PowerCon plugs supply juice from each channels's power supply to the amplifier chassis, while a third cable handles the control signal. You can't experiment with power cords---MF's AC socket is not the standard IEC connector but the higher-current version. The amp is not balanced, signal input is via a pair of RCA jacks. Speaker hookup is via dual pairs of steroidal custom-machined, gold-plated, solid brass multi-way posts fitted with huge, tri-knurled nuts.
While these connectors look impressive, they proved to be the Nu-Vista's single seriously annoying feature. The threaded post's diameter is so big, no spade-lug connector known to man can fit over it---you're left to insert one tip into the hole drilled through the threads for bare wire. When you try tightening the big nut, shovel-shaped spades will either need to be flattened (no thanks), or backed out of the hole enough so the nut can clamp onto the flat part, which reduces contact area. All in all, I feel this is a post design meant to please the eyes more than to fulfill the cable-connection requirements of a high-powered, high-current amp---eg, large contact and secure connection. Phooey.
Antony Michaelson solved the problem by sending along some excellent-sounding Nu-Vista interconnects and speaker cables fitted with banana plugs on one end, spade lugs on the other. Guess which end goes to the amplifier? (These wires deserve a separate review, which I hope to provide soon in a cable shoot-out.)