Nad 3155  - 3150

Ampli integrato


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Ampli Integrato

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55 watt





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Phono input

Input impedance (R and C) MM 47k½ / 100/200/320pF

MC 100½ / 1000pF

Input sensitivity, 1kHz MM 2.8mV

MC 0.28mV

Signal/Noise ratio (A-weighted with cartridge connected) MM 78dB ref. 5mV

MC 78dB ref. 0.5mV

THD (20Hz - 20kHz) <0.04%

RIAA response accuracy (20Hz - 20kHz) ±0.5dB

Line level inputs

Input impedance (R and C) 10k½ / 220pF

Input sensitivity (ref. 1W) 25mV

Maximum input signal >10V

Signal/Noise ratio (A-weighted ref 1W) 86dB

Frequency response 20Hz - 20kHz / ±0.5dB

Line level outputs

Output impedance Pre-amp 800½

Tape Source Z + 1k½

Maximum output level Pre-amp 10V

Tone controls

Treble ±7dB at 10kHz

Bass ±7dB at 100Hz

Bass EQ +3dB at 70Hz

+6dB at 32Hz

Infrasonic filter (switchable) -3dB at 15Hz - 12dB/octave


Continuous output power into 8½ * 55W (17.4dBW)

Rated distortion (THD 20Hz - 20kHz) 0.03%

Clipping power (maximum continuous power per channel) 65W

IHF Dynamic headroom at 8½ +3dB

IHF dynamic power (maximum short term power per channel) 8½ 100W

4½ 100W

2½ 130W

Damping factor (ref. 8½, 50Hz) >50

Input impedance 22k½

Input sensitivity (for rated power into 8½) 1.3V

THD (20Hz - 20kHz) <0.03%

Bridged Mode

Continuous output power into 8½ * 125W (21dBW)

IHF Dynamic headroom at 8½ +2.5dB

IHF dynamic power (maximum short term power per channel) 8½ 250W

Remote Yes

NAD Link Yes


Dimensions (W x H x D) 420 x 108 x 380mm

Net weight 8.4kg

Shipping weight 9.8kg

Power consumption (120 ~ 240V, 50/60Hz) 340W




NAD leads the audio industry in producing amplifiers with high-headroom circuitry and high-current

output stages, precisely the qualities needed for musically accurate reproduction of today’s wide-range

analogue and digital recordings. The 3155 integrated amplifier and the matching 2155 power amp are

the finest in a long tradition of highly praised NAD amplifiers, with increased power, improved reliability,

and numerous small refinements in both sound quality and ease of use.

The 3155 is two products in one. As a preamplifier it matches most separate audiophile preamps in

sonic performance and surpasses them in operating flexibility. As a high-current high-headroom power

amplifier it drives even “difficult” loudspeakers to surprisingly high volume levels with clean, solid, fullbodied

musical sound that remains refreshingly free from distortion even in transient peaks. The

combination of pre- and power amp, sharing one heavy-duty transformer and chassis, offers another

traditional NAD virtue: an impressive ratio of performance to price. The 2155, which is simply the power

amplifier section of the 3155 packaged on a separate chassis, is NAD’s “building-block” amp, offering a

variety of convenient and economical approaches to upgrading a stereo system for higher performance

and power. The 2155 is an obvious choice if you want to step up from a low-powered receiver or

integrated amp, or if you are using a separate preamplifier. If you need still higher power, a pair of

2155s in the “bridged” mode deliver nearly three times as much power output for only twice the cost.

The 3155 and 2155 deliver substantially more than their conservatively rated 55 watts/channel into the

complex and varying impedances of real loudspeakers. In the bridged monophonic mode each amplifier

is rated conservatively at 150 watts continuous output. And these amplifiers maintain a full 3 dB of IHF

dynamic headroom (2.5 dB in bridged mode), meaning that they deliver twice their rated power in brief

bursts: over 110 watts/channel in stereo and about 250 watts in bridged configuration. This headroom

for peaks is crucially important for reproducing the uncompressed transients in modern digital and DBXencoded


When combined as a bridged stereo pair, the 3155 and 2155 function as a 150 W/ch stereo amplifier

with 250 watts per channel of short-term output. That power, together with the remarkable flexibility

and flawless sonic performance of the 3155’s preamplifier section, makes the 3155/2155 combination a

remarkable best-buy system.

High Current and Headroom: Designing For Real-Use Conditions

Since amplifiers are usually rated in terms of a few standard specifications (e.g. 8-ohm power and THD),

many designers concentrate on optimising test-bench performance. But in the real world, amplifiers are

connected to loudspeakers with complex impedances, not to 8-ohm test resistors, and they are used to

play music, not sine-wave test tones. In NAD amplifiers every circuit is designed to deliver full

performance under real-use conditions. While many specific engineering goals follow from this principle,

two have been the cornerstones of every amplifier in NAD history (including the legendary Model 3020):

graceful handling of dynamic transients that exceed the amplifier’s rated power, and the ability to deliver

large bursts of output current to the loudspeakers. Electrical power is the product of voltage and

current, but it is the current flowing through the voice coil that causes a loudspeaker cone to vibrate

and reproduce sound. As NAD engineers have always known, and other manufacturers have lately

begun to realise, to obtain precise electromagnetic control of the speaker’s motion the amplifier must be

able to supply high peak currents upon demand, unconstricted by transistor “protection” circuits. The

NAD 3155/2155 amplifier circuit produces peak cur-rents of up to 40 amperes per channel.

Preamplifier Features (3155)

Digital-ready design.The amplifier’s line-level inputs will not be overloaded by high-level signal peaks

from a Compact Disc player or digital tape recorder. The 103 dB signal-to-noise ratio of the 3155

exceeds that of any analogue or digital program source. The low-impedance, low-noise design of the

volume and tone control circuits guarantees that the transparent clarity of the finest analogue and

digital recordings will be preserved.

The phono preamplifier, too, is audibly (and in some cases dramatically) quieter than most other preamp

circuits, not only with moving-magnet pickups but also with low-output moving coil cartridges. The

entire amplifier circuit has ample dynamic range for every program source, including the widest-range

digital Compact Discs. Ultra-quiet MM and MC phono preamp circuits. As long as LPs remain a principal

music source, there must be no compromise in the phono preamp. The phono circuit in the NAD 3155

employs ten selected transistors per channel to obtain the widest possible dynamic range with

outstanding freedom from noise and distortion at all signal levels. A differential FET input circuit ensures

ultra-low-noise operation at the high impedances of MM cartridges, and its linearity in the MegaHertz

range, aided by a custom-wound input filter, provides exceptional rejection of all interference from TV,

CB radio, and computers. A separate high-gain MC pre-preamp stage uses newly developed transistors

optimised for lowest noise with low MC impedances. A push-pull high-current output circuit drives the

precision RIAA equalisation network without slewing distortion, and its 107 dB dynamic range comfortably

accommodates all digitally-mastered LP recordings with room to spare.

Bass EQ

A special equalisation circuit provides 6 dB of boost at 32 Hz in order to strengthen and extend the

deep-bass response of closed-box loudspeaker systems.

A typical bookshelf speaker that rolls off below 50 Hz will have strong output to 30 Hz when used with

the NAD 3155, providing the sort of authentic bass “feel” that might otherwise require a costly separate

subwoofer system. Infrasonic filter, Precise infrasonic filtering is included to eliminate signal

contamination from turntable rumble, record warps, tonearm/stylus resonances, vibration and acoustic

feedback. This guarantees the cleanest possible handling of signals within the audible range and

eliminates the excessive woofer-cone excursions that can cause intermodulation distortion and muddy

bass in systems without filtering.

Power Amplifier Features (3155 and 2155)

Loudspeaker impedance matching. Standard lab tests of amplifiers use 8-ohm resistors in place of

loudspeakers, But most loudspeakers have a lower and more complex impedance that increases the

required amplifier output current. (And if you connect two pairs of loudspeakers, the effective

impedance of the pair is halved.) For this reason the 3155 and 2155 amplifiers are designed to deliver

their maximum power into low impedances of 4 or even 2 ohms. But the exclusive NAD impedance

selector allows you to re-optimise the amplifier circuit to produce greater output voltage, for the most

effective delivery of power to loud-speakers whose true impedance is 8 ohms or higher.

Soft Clipping

NAD’s trademarked Soft Clipping circuit gently limits the waveform when the amplifier is driven beyond

its maximum power rating. By preventing the out-put transistors from being driven fully into saturation,

the Soft Clipping reduces the harshness that is normally heard when an amplifier is overdriven. Because

of this and the amplifier’s high dynamic headroom, the sound remains clean and musical even at very

high sound levels, rather than being distorted as in other amplifiers.


If still more output power is needed, a bridging switch immediately converts the stereo amplifier into a

monophonic unit conservatively rated at 150 watts. A matching NAD 2155 power amplifier (also

bridged) can be used for the second stereo channel. With an IHF dynamic headroom of +2.5 dB in the

bridged mode, the 3155 and 2155 can produce peak levels of over 250 watts per channel for musical

transients. The combination of the 3155 and 2155 in bridged mode becomes, in effect, the world’s most

powerful integrated amplifier while retaining all of the operating simplicity of the 3155 amplifier alone.

Since the 3155 has independent preamp outputs and power amp inputs, it can also be used with an

electronic crossover for bi-amplification with either full-range speakers or a separate sub-woofer.

Exceptional Performance and Value

The 3155 amplifier represents the kind of value that has made NAD world-famous. With its flexible and

musically useful controls, its very low noise and wide dynamic range, its powerful high-current output

stage, its unique speaker-impedance matching for maximum power transfer, its “building block”

expansion options, and its consistently musical sound quality, the NAD 3155 is a strong con-tender for

the title of the best integrated amplifier in the world today.

The NAD 2155 is a superb general-purpose power amplifier with an unusually attractive ratio of

performance and power to price, and it is also the core of the unique NAD building-block concept that

allows the stereo system to evolve with your needs or your budget, now and in the future.