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The 2200 virtually redefines the concept of dynamic head-room.
Its high power reserves are available, not only for the short 20-millisecond bursts used in the standard
IHF dynamic headroom test, but also for musical surges and climaxes lasting ten times longer. Even with
compressed recordings of rock music in which the peaks may be only 8 dB higher than the average
power, that may be enough variation to allow the 2200 to operate at high efficiency and maintain a
clipping level above 500 watts per channel into the 4-ohm impedance that is typical of real speakers.
The appeal of the NAD 2200 may be based mainly on its combination of high dynamic power and low
cost, but there are other noteworthy aspects of its design, too.
Transparent sound
The audio circuitry of the 2200 is based on the same principles that gained worldwide praise for other
NAD amplifiers. In the 2200 the circuitry is scaled up substantially in speed and power, using the finest
selected parts available today-individually tested filter capacitors and ultra high-speed transistors for
wide bandwidth and extremely low distortion. The output stage is a fully complementary parallel circuit
using high-gain 25MHz transistors with over 10 times the “safe operating area” of transistors used in
typical 100 watts/channel designs.
High-voltage, high-current design
Current flowing through the voice-coil is what causes a speaker to produce sound, and NAD was the
first manufacturer to emphasise the importance of high output current capacity-unrestricted by so-called
protection circuits-to cope with the complex, reactive impatience that many speakers present. The NAD
2200 can produce peak output currents exceeding ±50 Amperes on demand, together with peak output
voltages of ±95 volts to handle the most dynamic signals.
Inverted channels for powerful bass
The greatest power demands commonly occur at low frequencies. Bass signals are in phase (and virtually
monophonic) in most recordings; thus when the bass waveform is strongly positive in the left channel, it
usually is strongly positive in the right channel at the same time. As a result both channels draw current
simultaneously from the positive half of the power supply, while the negative half sits idle. During the
negative half of the waveform, both channels draw from the negative supply while the positive supply
sits idle. In the NAD 2200 the right channel is internally inverted in polarity. When a bass waveform
causes the left channel to draw current from the positive supply, the right channel draws its bass power
from the negative supply, and vice-versa. This efficient usage halves the instantaneous drain on either
supply, allowing much stronger bass to be reproduced without draining the supply.
Bridging
The NAD 2200 is so powerful in the normal stereo mode that few listeners will ever need more. For
special situations the two channels of the 2200 can be bridged to form a mono amp of truly immense
power. Its rated continuous sine-wave output is 400 watts, while its dynamic power output exceeds
1200 watts into 8 ohms and 1600 watts into 4 ohms.
Two 2200s in bridged mode (delivering over 3 kilowatts into a pair of 4-ohm speakers) would cost about
the same as an ordinary 400-watt amplifier.
Quiet circuitry
The delicacy and purity of low-level musical information is as important for realism as the power to
handle climaxes. The signal-to-noise ratio of the 2200 (relative to its rated 100 W/ch output level) is
greater than Ill dB, No fan noise. In most power amps that are capable of the same 500 W/ch output on
musical signals as the 2200, a noisy fan must be used to dissipate excess heat from the circuitry.
The efficient 2200 is totally, blissfully silent in operation.
Close-tracking Soft Clipping™ The newly improved Soft Clipping” circuit in the 2200 accurately tracks
the available peak power, regardless of speaker impedance. Older Soft Clipping”” circuits tended to
reduce the available dynamic power by 1.5 to 2 dB in order to ensure that continuous output would
always be free from harsh distortion (even when the amplifier was over-driven).
With the new PowerTracker™ circuit, this limitation no longer applies. Now the amplifier’s sound
remains subjectively clean and transparent right up to the maximum output level. It continues to sound
good even at levels 2 to 3 dB above the amplifier’s rated maximum output, since the Soft Clipping
circuit gently rounds off the waveform corners and prevents any distortion due to power-supply
modulation as well as reducing high order harmonics which may damage tweeters.