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 4020A Tuner

The NAD 4020A is a rationally designed and built, at moderate price,  AM/FM tuner, whose performance in most locations and with most broadcasts is audibly identical to that of many more expensive  and elaborate tuners. The 4020's quality of sound is limited only by the quality of the transmitted broadcast.
Recent dramatic advances in FM tuner circuitry, particularly in the development of inexpensive but high-performance "building block" circuit modules, have been incorporated in the 4020A to provide excellent sound at reasonable price.

Such crucial design parameters as sensitivity, low distortion and wide stereo separation have been given priority over the inclusion of costly superfluous features and esoteric circuitry whose benefits are totally inaudible except in rxtreme reception conditions. But no compromises whatsoever have been made in those performance areas which relate directly to the 4020's listening quality in normal and even somewhat difficult reception locations.
High Sensitivity
The "front end" tuning circuit, for example, employs a Junction FET amplifier, for an optimum combination of sensitivity to weak signals and resistance to cross - modulation from strong signals. The intermediate frequency (I.F.) amplifier, a high-gain IC, provides excellent limiting (static suppression), very good AM rejection (suppression of multipath interference), and smooth muting of interstation noise.
Low Distortion
While budget-price tuners commonly contain one or two ceramic I.F. filters, the NAD 4020A employs a total of three. Their sharp selectivity minimises interference from adjacent stations on the increasingly crowded FM dial, and their linear-phase respponse contributes to minimum distortion of stereo broadcasts. Multiplex stereo decoding is performed by the latest phase-locked loop (PLL) IC. In addition to low noise and wide stereo separation, the PLL decoder yields the lowest distortion in stereo reception - in particular, minimum inter-modulation between high audio frequencies and the 19 kHz stereo pilot tone.
Wide Stereo Separation
It is important to maintain wide stereo separation at low and high frequencies as well as the commonly specified 1 kHz midrange point. In the 4020A phase shift of the composite signal is minimised in order to preserve full low-frequency separation, and a special NAD phase-compensated crosstalk cancellation circuit increases high-frequency separation and minimises any residual distortion.
Instead of a costly and fragile moving-coil tuning meter the 4020A has a set of three LED indicator lights which form a remarkably simple and accurate meter. Either of two amber LEDs illuminates when the 4020A is mistuned to either side of a station frequency, and a green LED illuminates when the station is optimally tuned for minimum distortion 9within 0,025 MHz). The brightness of the green tuning LED indicates the signal strength, when it is dim the station is too weak for optimum reception.

For the music lover seeking uncompromised performance for a modest investment, the NAD 4020A is the logical choice. There are more costly tuners available, some of which have more impressive specifications,, but very few sound better in everyday use.
FM Tuner Section
Input Sensitivity
Mono -30db Total Harmonic Distortion+N :  10,9 dBf (1,9 µV/75 Ω)
Mono 50 dB S/N :  16 dBf (3,5 µV/75 Ω)
Stereo 50 dB S/N :  37 dBf (40 µV/75 Ω)
Capture ratio :  1,5 dB (45 - 65 dBf)
AM Rejection:  60 dB (45 - 65 dBf)
Selectivity:  65 dB
Image Rejection:  50 dB
IF Rejection:  75 dB
Harmonic Distortion:
Mono :  0,2%
Stereo :  0,3%
Signal-to-Noise Ratio:
Mono :  75 dB
Stereo :  70 dB
Frequency Response:  30 Hz - 15 kHz ±0,5 dB
Channel Separation:  42 dB (at 1 kHz)
AM Tuner Section
Usable Sensitivity:  250 µV
Selectivity:  30 dB
Image Rejection:  50 dB
IF Rejection:  40 dB
Power Rating:  220 V, 50 Hz   or 110 V, 60 Hz
Dimensions (W x H x D):  420 x 96 x 240 mm
Weight [Net/Shipping]:  4,2 kg / 5,6 kg

Nessun commento:

Posta un commento