Предусилители — Naim NAC 552

The NAC 552 is a stereo preamplifier from Naim Audio built as two boxes, a control unit and the separate 552 PS power supply. It first appeared in 2002, and Naim has since updated the supply with its Discrete Regulator technology. The split into two boxes follows the same approach that Naim uses for its top power amplifiers, where the transformer is kept apart from the signal circuits.

Key specs that matter

The control unit provides seven DIN inputs and two RCA inputs, and two of the inputs can be configured to run at unity gain. Gain is 29 dB, with maximum volume reached at the 22 dB mark. Power consumption is 15 W in normal use, below 0.5 W in standby, below 2 W in network standby and below 0.3 W when switched off, and a user-selectable automatic standby after 2 hours can be turned on or off. Mains input is 115 V or 230 V at 50 or 60 Hz through a Naim PowerLine cable. The head unit measures 432 mm wide, 87 mm high and 314 mm deep, and weighs 12.9 kg.

Engineering and use context

Moving the transformer out of the control unit is meant to give better rejection of electromagnetic interference. In the 552 PS a split-rail design, with separate positive and negative supplies, uses an 800 VA toroidal transformer, three smoothing capacitors and a Discrete Regulator stage. Inside the control unit the circuit boards sit on a fully suspended sub-chassis resting on coil springs, which isolates them from vibration reaching the case. Volume and balance are set with precision rotary potentiometers, and the volume pot is microchip controlled so that the supplied remote handset can operate it. Independent listen and record banks let one source be recorded while another is played, and inputs can be assigned to suit the connected components.

Pairing

The large bank of DIN inputs is aimed at Naim sources and phono stages, while the RCA pair covers components from other makers. An AV bypass mode lets the preamplifier sit inside an existing AV system, so a stereo setup and a home cinema processor can share one pair of loudspeakers, and the unity-gain inputs suit other sources that carry their own volume control. On the power amplifier side it can be combined with a two-box Naim design such as the NAP 500 DR, which shares the separate supply approach.

Alternatives

The Naim NAC 332 from the New Classic range is a two-channel preamplifier that can also power the NVC TT phono stage.