NAD Masters Series M25, Owner'S Manual, Page: 6 / 54

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ABOUT THE M25
Designed specifically for home theatre and custom installation set-ups,
the NAD M25 Power Amplifier delivers uncompromising performance.
It combines supreme reliability, flexibility, and performance with
outstanding value. Flexibility has always been an important part of
NAD components. Such flexibility is particularly important in home
theatre and other multi-channel systems. That’s because it is common
for a multi-channel system to incorporate different brands and models
of loudspeakers. Often these speakers have different levels of
efficiency. The individual input level controls for the seven channels of
the NAD M25 make it easy to compensate for such differences in
efficiency, and achieve the ideal system balance. Ample dynamic
headroom of the M25 ensures that the very wide dynamic range of
modern cinema soundtracks and digital music sources will be
preserved. In addition, the M25 will handle low impedance speakers
with ease.
The M25 incorporates NAD’s unique Soft-Clipping circuitry in all seven
channels. Any amplifier can be overdriven if it is played too loud,
exceeding the maximum output power. Under such circumstances,
amplifiers produce extreme high levels of distortion which, besides
sounding very unpleasant, can damage your loudspeakers. The Soft
Clipping circuit suppresses such distortion and minimizes the risk of
damage to speakers. This is particularly important with movie
soundtracks which often contain very dynamic outbursts in which,
unlike music, it is difficult to hear this potentially damaging distortion.
The Soft Clipping LED on the front panel illuminates when the Soft
Clipping circuit is engaged. Soft Clipping can be defeated with a rear
panel switch.
The 12V trigger connection on the back panel allows the amplifier to
be switched from On to Stand-by and vice-versa remotely. This way,
the M25 can be part of a system which can be turned on and off with
a single command, easing operation. The 12V trigger also allows the
amplifier to be installed in places not in easy reach.
THE DESIGN
The NAD M25 houses seven individual amplifiers, each on separate
circuit board. Each amplifier channel acts as a “mono block” within
the chassis. Each input connector, and set of loudspeaker output
terminals, is directly connected to that channel’s circuit board. This
design eliminates extra wiring and keeps signal paths short.
Furthermore, this modular design increases reliability and thermal
efficiency. The input circuit uses a totally new dual differential input
topology that operates in true Class-A mode. The special Holmgren™
toroidal transformer has less hum and magnetic leakage than
conventional toroidal transformers, but retains the usual benefits of
high efficiency and high power-to-weight ratio.
Ruggedness and reliability are critical in custom-installed systems. The
M25 uses a combination of fuses and non-intrusive electronic
protection. This provides highly effective protection that does not
effect audio performance. Each channel is protected against excess
temperature, DC fault and loudspeaker short-circuit. The M25’s
inherently conservative, high-voltage/high-current output stage has
been designed for years of trouble-free service.
NAD was the first company to introduce a THX® Certified power
amplifier. In that tradition, the M25 easily passes THX Ltd.s' stringent
THX® performance requirements. As a result the NAD M25 will
handle the most demanding signals with ease, and yet preserve every
subtle audio detail in the most demanding THX® Ultra2™ Surround
systems. THX and Ultra2 are trademarks or registered trademarks of
THX Ltd. All rights reserved.
POWERDRIVE
To meet the diverse requirements of high current drive and high
dynamic power, our patented PowerDrive amplifier circuit will build
further on our reputation for amazingly effective power. By adding a
second high-voltage rail to our well regulated high-current power
supply, we get an "overdrive" that can nearly double the continuous
power on a short term dynamic power basis. This is a further
development and refinement of our renowned Power Envelope circuit,
utilized by NAD in the 80's and 90's. PowerDrive differs from Power
Envelope in that it offers greater amplifier stability and low impedance
drive capability, resulting in less distortion when driving real speakers
with real program material
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