NAD Masters Series M3 - Manual (Page 2)

and mono settings. Tone controls offer bass and treble
adjustment, as well as a ‘spectral tilt’ option that is highly
effective at correcting the tonal balance of many recordings
by simultaneously increasing the bass and decreasing the
treble (and vice versa) to create a warmer (or cooler) balance.
We have also included a second set of preamp outputs
and a switchable high pass fi lter for the internal amplifi er,
to allow easy implementation of an active subwoofer or
biamplifi cation.
The rugged chassis is built using thick 2mm mild steel
plates with a front panel employing extruded aluminum
and die-cast zinc in its construction. Special attention
was paid to the control of mechanical resonance, as this
can affect sonic performance. Special isolation feet use
aluminum and silicon rubber in a vibration damping
confi guration. All signal connectors are heavy duty gold
plated types specifi cally engineered for the NAD Masters
Series components. Finished inside and out, the M3 utilizes
powder coating and advanced automotive paint fi nishes,
creating an enduring and elegant mechanical package.
PREAMP DESIGN
The preamp uses all discrete low noise high impedance J-
FET buffer amps and very high quality reed relay switches
at the preamp input. Special high current low output
impedance Class A gain modules provide tremendous
dynamic headroom and high output current, combined with
a exceptional S/N ratio in excess of -100dB (IHF).
The volume attenuator is very unique in that it uses discrete
1% precision resistors that keep impedance (and noise) very
low. It is arrayed in 3 stages to reduce the residual noise in
each amplifying stage and prevent the ‘cascade effect’ of
noise that is present in most preamp designs. This circuit
also provides the balance control, and as a result channel
separation is superb and inter-channel cross talk is virtually
eliminated. These resistor arrays are switched using 15
volt digital switches under software control, keeping all
attenuation at the ideal point in the circuit architecture.
Low impedance stepped tone controls provide +/- 5 db
of boost/cut in the bass and treble regions, or can be
confi gured to provide variable slope, or ‘spectrum tilt’ at +/-
3dB per decade.
Biamp function allows the use of a second amplifi er or
active subwoofer PreOut 2, and offers a high pass fi lter
function on PreOut 1, with selectable 40Hz, 60Hz, 80Hz,
100Hz or Full Range options. These are analog 2nd order
fi lters confi gured around the low impedance differential
Class A output stage of the preamp. This output stage also
employs proprietary distortion cancellation circuitry.
A balanced line input is also provided using identical JFET
buffers feeding a discrete differential amp and yielding
common mode rejection in excess of 80dB.
Separately regulated DC supplies are derived from the
dual mono power supply. Copper buss bars and discrete
regulators keep circuit noise to an absolute minimum
throughout. The display and digital functions operate from
an independent power supply to prevent any interference
with the analog signal path.
POWER AMP HIGHLIGHTS
The M3 features a Dual Mono design with separate
unregulated, and discrete regulated supplies for different
stages of the 2 channels. The twin custom-made “Holmgren”
toroidal transformers use proprietary magnetic shielding
technology. High current rectifi ers feed low ESR 105C fi lter
capacitors.
NAD’s PowerDrive technology measures load impedance
continuously on each channel and adjusts the power supply
voltage for maximum undistorted dynamic power into the
connected speaker at all times and under all operating
conditions. The signal processor also continuously
measures temperature and average long term power and,
based on this information, chooses the optimum voltage.
PowerDrive allows the M3 to sound far more powerful than
its already impressive 180 watt per channel rating would
suggest. Totally effortless sound, even at elevated levels, is
the hallmark of the PowerDrive amplifi er.
The M3 utilizes a wideband current-mode Class A voltage
amp featuring large open loop compensated bandwidth,
and running from low noise stabilised power supplies.
NAD’s patented current amp output stage starts with < 0.02
% static and dynamic distortion open loop (before feedback),
even into 3 ohms at 20-20k at all levels. By utilizing small
amounts of feedback the circuit returns distortion levels
at all audible frequencies that are at limit of measurement
– less than 0.002%!
The super rugged output stage features 4 pairs of 150W
discrete bipolar output transistors per channel, for 50A peak
undistorted output current. Massive heat sinking assures a
lifetime of trouble free operation.