Naim NAP 500 Power Amplifier / 500 PS Power Supply (2006)

Here we have a fantastic power amplifier from British experts Naim Audio. The NAP 500 was their top of the range unit when launched in 2000 and continued as such until the Naim Statement came along in 2014. It is still in production today and is much sought after. Our unit dates from 2006 and comes in very good condition along with its similarly styled power supply unit the NAP 500 PS. There are a couple of very small cosmetic blemishes – please see photographs.
Both units are supplied in original factory packaging along with mains cable, burndy cables, 4 Pin DIN to XLR cables and our standard three month warranty.
Naim Say….
The design brief for the NAP 500 required an amplifier that could drive any load down to 2 ohms for prolonged periods, deliver over 100 W into 8 Ohms and sound at the very least, as good as our existing reference, the NAP 135.
If the compromises implied by the use of multiple sets of output devices, either in totem-pole or parallel configuration, were to be avoided the search was on for a very special output transistor. A bipolar transistor with a specification combination of very high current, power rating and bandwidth was needed, far in excess of anything available to Naim before. A suitable output device was eventually developed after six years’ collaboration with a semiconductor manufacturer.
From an early stage of conception it was decided to use bridged amplifiers for each channel of the NAP 500. This allowed the design to have maximised open and closed loop speed, less intrusive protection circuitry and reduced interaction between input and output signals as the very high drive currents to the loudspeaker do not flow through the system earth.
Naim has always understood the importance of reducing supply-induced intermodulation distortions and mains harmonic electrical noise from an amplifier, and has always used regulated supplies in its premier amplifiers. It was considered likely that improvements in these areas would yield further large gains in performance. Each channel of the NAP 500 includes ten stages of local regulation. To reduce interference from the mains supply further, the transformer and first stages of the power supply are in a separate enclosure (the same size as a SuperCap), which provides twelve raw D.C. supplies for the power amplifier. Hence, the NAP 500 system consists of two boxes, a stereo amplifier and a separate power supply.
All new circuit topology has been developed to maximise bandwidth and reduce distortions and power supply dependency. Also, special attention has been paid to reducing thermally-induced noise, an especially important consideration in power amplifiers. A variable speed intelligent fan system provides discreet extra cooling if needed.
When measured, the performance of the finished amplifier exceeds the design brief in all areas.
Power output per channel is over 140W into 8 ohms and compared with the NAP 135, which in itself already provided exemplary measurements, the NAP 500 has five times the internal bandwidth, a quarter of the distortion and a one hundred times reduced operating noise floor.
Perhaps needless to say, every aspect of its sound quality is truly exceptional.
The 500 power supply has been designed as a no compromise power source for the amplifier. It has a transformer with six secondary windings each charging two reservoir capacitors providing twelve independent voltages in all. If the 500 is used with two supplies, three secondary windings and six capacitors in each supply are unused. These unused parts of the circuit take small but parasitic currents from the mains and this disturbs the correct operation of the six used supplies, degrading performance.
Specifications:
Power Output: 140 W/Ch 8Ω
Voltage Gain: +29 dB
Input Impedance: 18 kΩ
Frequency Response: 1.5 Hz – 100 kHz
Mains Supply: 100 V; 115 V; 230 V, 50 or 60 Hz
Dimensions: 432 (W) x 375 (D) x 160 (H) mm; Power supply unit: 432 (W) x 314 (D) x 87 (H) mm
Weight: 25.0 kg; Power supply unit: 15.4 kg

To read a review from Hi-Fi News magazine please click here