4020A
AM/FM Tuner
Date of manufacture : ? - Jan 81
Please note that this document contains the text from the original product brochure, and some technical statements may now be out of date
The NAD 4020A is a rationally-engineered, moderately- priced 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 a 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 extreme 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-priced 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 response 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 (within 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.
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