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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 p/- 5 db of boost/cut in the bass and
treble regions, or can be configured to provide variable slope, or 'spectrum tilt' at +/-
3dB per octave.
Biamp function allows the use of a second amplifier or active subwoofer
PREOUT 1
,
and offers a high pass filter function on
PREOUT 2
, with selectable 40Hz, 60Hz, 80Hz,
100Hz or Full Range options. These are analog 2nd order filters configured 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 custom wound Toroidal
transformers use proprietary magnetic shielding technology. High current rectifiers
feed low ESR 105C filter 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 amplifier.
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.
About the M3 Dual Mono Integrated Amplifier:
Introduction
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