NAD Masters Series M25 User manual

The Masters Series – M25 Seven Channel Power Amplifier
- THX Ultra 2 Certified
- 7 X 160 watts Full Disclosure Power,
20Hz - 20kHz, at less than 0.03% THD with all
channels driven simultaneously into 8/4 Ohms
- PowerDrive™
- Dynamic power of 220 watts at 8 Ohms, 385
watts at 4 Ohms, and 485 watts at 2 Ohms
- NAD’s Custom-Made “Holmgren” transformer
- NAD Soft Clipping™
- Precision low noise Input Level Controls
- Custom 5 way Binding Posts
- 12V Trigger for advanced control options, 1 in
- Detachable AC cord
MASSIVE POWER
More power is always better when it comes to sound quality. Power is
required not only to play loudly, but also to play cleanly without audible
distortion. When an amplifier is asked for more power than it was
designed to deliver, it can only respond with distortion.
Fortunately the M25 is one of the most powerful amplifiers on the market
today designed for home use. With a minimum of 160 continuous watts
per channel, all channels driven simultaneously, from 20Hz to 20kHz at
rated distortion of 0.03%, the M25 easily delivers lifelike sound levels
even in large home theatre rooms. It handily meets THX’s most stringent
certification level, Ultra 2.
Unlike most surround sound receivers (NAD’s own receivers are a
rare exception) that only rate power with 1 or 2 channels running, or
use very short term measurements, the M25 can deliver its full rated
power continuously for hours on end. Custom designed heat sinks and
thermostatically regulated variable speed fans keep things cool under the
most severe operating conditions. A unique fan circuit that tracks signal
level, actually shuts down the fans during quiet passages to prevent any
mechanical noise from interfering with the program material.
But it’s not just the quantity of power that is important, it is also the quality
of power that determines whether you can hear just a fiddle sound, or the
unique character of a Stradivarius violin.
SOPHISTICATED CIRCUITRY
The M25 is comprised of 7 individual ‘Monoblock’ amplifier channels. Each
channel uses a balanced junction FET input stage resulting in exceptionally
low levels of noise and distortion. NAD employs a unique electronic
ground isolation circuit to prevent ground loop noise in the system – a
common problem in complex multi-channel systems. This circuit offers
high input impedance for negligible loading on source components which
results in less noise and distortion in the real world.
A fully complementary differential class A voltage amp with a push pull
cascode output stage, provides ample current to drive the triple emitter-
follower output stage. This circuit topology offers very low distortion
combined with high current capability.

NAD’s PowerDrive™ circuitry measures each channel’s
dynamic impedance individually and computes the optimum
power supply voltage required to drive the output stage for
maximum power and effi ciency. PowerDrive permits high
dynamic power and low impedance drive capability, while
maintaining ultra low (<0.03%) levels of distortion.
The M25 also incorporates NAD’s acclaimed switchable
“Soft Clipping” circuit. Each channel has individual over
current, DC, infrasonic and ultrasonic overload sensing
and protection for complete reliability under even the most
severe operating conditions.
MASSIVE POWER SUPPLY
The M25 utilizes NAD’s proven Holmgren Toroidal
transformer design, in a massive size, to create a power
supply that offers very well regulated voltage, and truly
massive amounts of current. The Holmgren transformer
design utilizes proprietary low leakage fi eld technology
which is very low in both electrical noise (stray fi eld) and
physical noise (buzz).
Multiple 100,000 uF, 100V low ESR capacitors ensure a clean
DC voltage supply for very low noise and truly explosive
dynamics. Ultra low impedance copper buss bars are used
exclusively throughout for power delivery and grounding.
DETAIL ENGINEERING
It is the many small details that differentiate a really great
amplifi er from a merely adequate one. Buffered low
impedance level controls allow system fi ne tuning without
the distortion typical of most level control circuits. Custom
designed gold plated speaker binding posts offer multiple
connector options, while maintaining a large, corrosion-
free, low impedance contact area. Input jacks are also
custom designed for maximum performance. Even the feet
that support the M25 are engineered to fi lter out vibration
and provide maximum performance.
PUTTING IT ALL TOGETHER
The highly developed, yet elegantly simple circuitry of the
M25, is matched with a brute force power supply to create
one of the most powerful Home Theatre amplifi ers on the
market today. Yet all this power is balanced by a liquid
and transparent sonic signature that is subtlety nuanced
and insightful. The M25 simply adds another dimension to
surround sound that must be heard to be believed.

Continuous Power, 20Hz-20kHz, all channels
driven simultaneously at 4/8 ohms
Rated Distortion (THD 20Hz-20kHz)
Clipping Power (0.1% THD)
IHF dynamic headroom at 4 ohms
IHF dynamic power at 8 ohms
IHF dynamic power at 4 ohms
IHF dynamic power at 2 ohms
Damping Factor
Input Impedance
Input Sensitivity
Voltage Gain
Frequency Response
Signal/Noise Ratio
Dimensions (W x H x D)
Net Weight
Shipping Weight
>160 W (22.0 dBW)
0.03%
>180 W
3.9dBW
>220 W (23.4 dBW)
>385 W (25.9 dBW)
>485 W (26.9 dBW)
ref. 8 ohms, 50Hz >180
1 Mohms;C = 180 pF
1250mV+/-50mV
29.0dB
20 Hz – 20 kHz ±0.2 dB
- 3dB at 3 Hz/70 kHz
>96 dB ref. 1 W
>118 dB ref. 160W
17 x 7 7/8 x 18 3/8”
435 x 200 x 465.6mm
96.3 lbs (43.7 kg)
112.3 lbs (51.0 kg)
Preliminary Specifications

NAD Electronics International reserves the right to change specifications or features without notice as design improvements are incorporated. NAD is a registered
trademark of NAD Electronics Internat�
written permission of NAD Electronics. International. Printed in Canada 05/05. www.NADelectronics.com