NAD 2200 brochure Transparent sound, High-voltage, high-current design, Bridging, Quiet circuitry

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.