"It all started from our customers who could not use Nagra amplifiers, like the acclaimed Nagra MSA, in their bigger systems because they needed more power to accommodate demanding speakers or a very large room. They were frustrated to mix and match Nagra sources, such as the HD DAC, with other brands for amplification.
Early in the development stage, we realize that we could push the limits of what is possible to achieve in an amplifier, if we allowed ourselves to have a larger chassis. We took inspiration from the world-acclaimed Nagra VPA amplifier and designed elegant tower-shaped monoblocks.
The power supply goes to extremes to make sure the amplifier is stable and can deliver high power at any time. It is built around a 1600 VA transformer. In Nagra’s own tradition it is followed by a multiple diode stage and a very complex dual PI filter. This allows the amplifier voltage rails to be extremely stable. In addition, the current draw from the HD AMP is not polluted by impulse signals. So the rest of the set-up can perform at its best. The dual Pi filter acts like a protection shield between the HD AMP and the mains.
The Nagra HD AMP audio amplification stage is relatively simple in its conception; this is in part what makes it so transparent and direct. Actually, each stage has been tuned to reach striking results. The driver stage for instance features numerous decoupling capacitors of different technologies. It has a very low output impedance to make the most of the power MOSFETs that follow.
Like all its famous predecessors in Nagra range, the HD AMP, uses MOSFET, field effect transistors. They are the closest thing to a valve triode and you can definitely feel its sonic character: direct, fast and musical. The HD AMP has precisely matched clusters of MOSFET, to insure the purest reproduction.
The Nagra HD AMP is fitted with a traditional Nagra Modulometer on the front panel, showing the output power."