Интегральные усилители — Musical Fidelity NU-VISTA 800.2

The Nu-Vista 800.2 is a hybrid integrated amplifier from Musical Fidelity that combines nuvistors with bipolar transistors. A nuvistor is a miniature small-signal vacuum tube housed in a metal and ceramic case instead of a glass bulb, and is said to be good for 100,000 hours of use. These tubes were mass produced in the late 1950s and early 1960s. Four 7586-type 6S51N nuvistors form a Class A tube stage ahead of a dual mono output section inspired by the TITAN design. The UK list price was GBP 10,999, and the model is now no longer available.

Key specs that matter

Output is 330 W per channel into 8 ohms and 500 W into 4 ohms, with 1000 W peaks into 2 ohms. Output voltage is 52 V RMS from 20 Hz to 20 kHz, clipping begins at 147 V peak to peak, and output current reaches 120 A peak to peak. THD plus noise is 0.005 percent typical across 20 Hz to 20 kHz, signal to noise exceeds 107 dB A-weighted, and response spans 10 Hz to 30 kHz within plus 0 and minus 0.1 dB. Damping factor is 200. The chassis is 483 x 187 x 510 mm and weighs 41 kg net.

Engineering and use context

Five output device pairs per channel, running in Class AB, sit in a locally decoupled output stage. The Nu-Vista 600.2 is built on the same platform. Power comes from oversized toroidal transformers and multi-array supplies, rewound for lower standing flux to reduce sensitivity to DC offset on the mains. Milled aluminium panels form a Faraday cage around the circuitry for electromagnetic shielding and resist vibration. Volume is set by a laser-trimmed control with a gain error of plus or minus 0.5 dB, and the front plate carries a VU meter display. The remote handset can switch the amplifier between on and standby, and the finish options are black or silver. Standby draw is 0.5 W, with a maximum of 900 W.

Pairing

Four RCA pairs at 40 kohm and one balanced XLR pair accept line sources. There is no phono or digital input, so a turntable requires its own phono preamplifier and digital sources an external DAC. Fixed and variable RCA outputs are provided, with the variable pair available for an active subwoofer or extra power amplifier. The 2 ohm peak rating shows the output stage is designed for difficult loudspeaker loads.

Alternatives

The Musical Fidelity Nu-Vista 600.2 is the smaller integrated model in the same series, also built around a nuvistor Class A stage.