What is stereo?

There are now two system of high fidelity, monophonic (monaural) and stereophonic. Monophonic is a system that starts from one microphone and is fed through a single high fidelity set. Stereophonic is a double system. Two separate microphones are placed at different sides of the orchestra and two different systems are used to keep the two signals or channels separated. Two separate speakers are used, placed on different sides of you room. Stereo is much like 3-D photography, two slightly different sound reach your ears giving you a new dimension in sound.

H.H. Scott '59

NAD 3020

 The NAD (New Acoustic Dimension) brand name has existed in Europe for about many years but is probably unfamiliar to most American audiophiles. NAD is an unusual company, involving an international group of independent dealers whose needs and suggestions play a major part in the development of its products, which are designed to sound as good as the state-of-the-art. Permits and to sell at prices within the reach of a broad segment of the buying public.
In designing its Model 3020 integrated amplifier. NAD began with the assumption that, for a given power-output level, a state-of-th-art. Unit need not cost significantly more than a poor or mediocre one. They focused on the design areas that can cause listening problems - for example, protective circuits that cause distortion with very low or highly reactive speaker loads, phono preamplifiers whose circuits interact with phono-cartridge inductance to affect high-frequency response, and circuits whose excessive bandwidth mekes them vulnerable to interference from radio transmitters and overload from infrasonic turntable rumble or disc warps.
 The NAD 3020 is a no-frills, moderately-prieced amplifier designed to provide state-of-the-art. Performance at volume levels far in excess of what would be expected from its conservative 20-watt per channel power rating. This remarkable characteristic is made possible by high-voltage, high-current output stages which can deliver short-term burst of two to five times the rated continuous power output into loudspeakers of widely varying impedances. The 3020's exclusive "Soft Clipping" circuit permits listening levels even beyond these limits by reducing harshness aat high volume settings.
The phono preamplifier section of the 3020 contains a sophisticated 6=transistor circuit which has been enginereed for extremely low noise and nearly distortion-free performance. Built-in infrasonic and ultrasonic filters further reduce the interference of non musical signals caused by turntable rumble, floor vibration, tone arm or stylus resonances.
These uniquely designed input and output stages combine to create an inexpensive amplifier which is easily capable of driving the very best loudspeakers.
 Designed for Real_Word Performance
If you read specificatoions and test reports you will find that the majority of modern amplifiers measure well on the test bench, with impressive figures for signal-to-noise ratio, power output at 8 ohmsm and ultra-low harmonic distortion. But outside the laboratory many of these products don't perform as well as their specifications suggest. In the home you don't listen tosignal generators and 8 ohms test resistors; you listen to complex musical waveforms generated by phono cartridges and reproduced through loudspeakers whose impedance is seldom 8 ohms.
Rather than incorporating costly refinements that may test well, but yeld little audible improvement, NAD's engineers have designed the 3020 for optimum performance in every day use.
 Effective Control Features
Like every other part of its design, the 3020's controls have been carefully considered for genuine usefulness. The Bass and Treble controls are tailored for musically effective response in the high and low frequencies without altering the critical mid-range tonal balance.
For listening at low volume levels or with sensitive headphones, the 3020's Audio Muting button reduces levels by 20 dB, expanding the useful range of the Volume control and subduing any residual circuit noise. A simple, elegant set of five LED's accurately displays the peak power level which the amplifier is delivering to the loudspeakers, form 1 to 35 watts into 8 ohms or 2 to 70 watts into 4 ohms. The circuit monitors both channels and displays the higher output at each instant.
 High-Performance Design
Wide Range Phono Preamplifier
In a moderately priced amplifier you might expect to find an economy preamp circuit, but the NAD 3020 contains a phono preamp stage which is audibly identical to the finest separate professional preamps. The 3020 preamp interfaces correctly with the impedances of real phono cartridges (as many preamps do not), it is quiet enough for use with either moving-magnet or high-output moving-coil pickups, and its distortion is extremely low, not only with sine-wave test tones but also when reproducing complex high-level music signals. The 3020 was designed to achieve the best signal/noise ratio when a cartridge is plugged in (rather than with the usual, but inappropriate, short-circuit input). The total dynamic range of the 3020 is typically 107dB, ample even for the digitally-mastered recordings of the 1980s.

Infrasonic and Ultrasonic Filters
Audio signals are often contaminated with interference at frequencies below and above the audible range, such as acoustic feedback, disc warps and radio interference. Amplification of such signals yields no sonic benefit, wastes amplifier power, and may cause intermodulation distortion muddy bass, excessive woofer cone motions, and even tweeter burnout. The NAD 3020 contains a precise, minimum-phase audio-bandpass filter which strips off such interference and preserves a clean musical waveform.
 Dual-Mode Power Supply
The power supply circuit for the output stage is only loosely regulated, so it is free to supply the high voltages needed for a high IHF headroom factor (at 8 ohms) and also to supply the large currents at lower voltages needed for driving low-impedance loads (down to 2 ohms). An entirely separate power supply circuit, operating from another secondary winding on the power transformer, supplies extremely stable, noise-free, regulated operating voltages for the preamplifier and tone control stages; thus distortion and blurring of the stereo image due to power supply modulation cannot occur in the 3020. The NAD 3020 has earned a world-wide reputation among audio reviewers for its sensible and efficient design and superb performance.
Numerous test reports, comparing the 3020 with equipment of far greater power rating and cost have proven the 3020 to be an outstanding value.
 The power supply for the NAD 3020 output stages is loosely regulated - that is, when there is little or no audio signal present, the supply voltage is relatively high, giving the amplifier a large short-term power-output capability (which is reflected in its very high IHF dynamic-headroom rating). A heavy load, whether from high average signal levels or from aa very low load impedance, causes the power supply voltage to drop, limiting the current through the output transistors to a safe value.
Pre-Amp Section
Phono Input
Input Impedance (R and C):  47 kΩ/ 47pF
Input Sensitivity (1kHz):  2.5 mV ref. 20W
Signal-to-Noise Ratio (A-weighted with cartridge connected):  75 dB ref. 5mV
Line Level Inputs
Signal-To-Noise Ratio (A-weighted ref 1W):   greater than 86 dB
Channel Separation:  greaer than 60 dB
Frequency Response:  20 Hz - 20 kHz (±0.5 dB)
Infrasonic Filter:  -3 dB at 15 Hz, 24 dB/octave
Ultrasonic Filter:  -3 dB at 35 kHz, 12 dB/octave
Power  Amp Section
Continuous Output Power (into 8 W )*:  20 W (13 dBW)
Rated Distortion (THD 20Hz - 20kHz):  0.02%
Clipping Power (maximum continuous power per channel):  30W
IHF Dynamic Headroom (at 8W):  +3 dB
IHF Dynamic Power (maximum short term power per channel):
40 W at 8 Ω
58 W at 4 Ω
72 W at 2 Ω
Physical  Specifications
Dimensions (W x H x D):  420 x 96 x 240 mm
Net Weight:  5,3 kg

Shipping Weight:  6,7 kg

Nessun commento:

Posta un commento