NAD T955 Amplifier
When someone talks about the advantages of a separate power amplifier over AV receivers, he usually notices that the sound always improves if the input stages and processors sensitive to the crosstalk are located at a distance from sources of strong electromagnetic fields. This is true - with a significant and rapidly changing current supplied to the load, not only transformers, but also power buses begin to "radiate". But this is only one argument in favor of separate amplification. The second, no less important point is that the digital part of most AV receivers becomes obsolete pretty soon - new sound standards, algorithms and interfaces appear. For example, today reputable sources are equipped with HDMI connectors, but you will not find them in receivers released just a couple of years ago. So we have to change the complex, expensive and, what is most offensive, good-sounding apparatus due to the fact that its preliminary part has ceased to meet modern requirements. In general, the idea is clear: having pushed a decent power amplifier into the rack, you don't have to worry much about the future, since the new processor will cost less in any case.
Obviously, with an eye to such forward-looking movie buffs, NAD has released the top model of T955 5-channel amplifier. This 20 kg block is capable to deliver for a long time 5x100W of power to the load with vanishing small distortions. Serious characteristics were achieved using proprietary circuitry and a special design. Each channel is assembled on a separate board and has its own, huge heat sink. Moreover, all channels are powered by separate transformer windings.
As you know, the sound of any amplifier is at least 50% determined by the power source. NAD T955 implements the proprietary PowerDrive principle, as evidenced by the PD logo on the front panel. A special circuit in dynamic mode evaluates the need of each channel and instantly changes the voltage on the buses of the output stage. In addition, there is a Soft Clipping switch on the back wall, which limits the output signal level.
The sound path is completely assembled on discrete elements, two powerful transistors are parallelized in each arm of the output stage. The topology and circuitry here are about the same as in the stereo models NAD C352 and C372.
All that is lacking is to add that NAD T955 provides for switching on and off from a 12-volt trigger, making possible to integrate it into a system with centralized control.
When turned on, 5 LEDs light up on the front panel, which after a few seconds change color to blue. This means that all channels have reached the operating mode, and there are no short circuits in the load. After a half-hour warm-up, I put the most characteristic, in relation to sound, scenes from Terminator 3. Rumble, rattle of metal, beats and sounds of shots at maximum volume are reproduced without compression. At the same time, the picture is very distinct and full of details - both timbral and dynamic. The smallest nuances are not lost against the general background, they are perfectly distinguishable in space. It is almost impossible to overload the amplifier even with very "tight" acoustics, it is completely not afraid of low-impedance load. When you activate Soft Clipping, the dynamic range is somewhat limited, but at extreme levels the ear does not notice the characteristic distortions that usually occur when the output stage is overloaded. The amplifier is noticeably heated, so during installation it is necessary to provide natural ventilation.
