Pioneer SX-939 Operating Instructions Manual page 3

SX-939 FEATURES
FM Front End With Dual-Gate FET's, Buffer Amp
FM tuner's sensitivity, overload resistance (ability to receive
very strong signals without distortion), image rejection and
spurious rejection are determined chiefly by the front end.
In the SX-939) latest components and circuit technology
have been employed to bring all these values close to their
theoretical limits: two dual-gate MOS FET's. RF amplifi-
cation, and the inclusion of a buffer amplifier between local
oscillator and mixer stage. In all performance character-
istics, the SX-939's FM tuner compares favorably with the
world's most advanced specialized tuners,
It hardly needs to be mentioned that the FM dial is of
course divided into equal "linear" intervals and that dual
tuning meters — signal strength meter and zero-center meter
—are provided for easy, precise tuning.
Ceramic Filters And IC's In IF Stages For
Sharp Selectivity
A total of three ceramic filters in the IF (intermediate
frequency) stages give sharp selectivity and never need to be
realigned. Integrated circuits functioning as limiters provide
stable operation and excellent capture ratio (the ability to
distinguish between a wanted and an unwanted signal on
the same station band).
Quadrature Detection, Phase Lock Loop (PLL)
Stereo Demodulator
Detection of the frequency-modulated signal is performed
by the "quadrature" method with a balanced-bridge type
differential amp, This costly design assures linearity
throughout the frequency band and reduces distortion to
the minimum, In the MPX circuit, a phase-lock-loop (PLL)
circuit design is used to give clear, stable separation at any
audio frequency. The circuit is equipped with an IC
(replacing six transistors) in a bridge configuration.
IC Mean Great AM Listening, Too
This section also incorporates integrated circuits and auto-
matic gain control in the RF and IF stages, as well as a
3-ganged variable capacitors for improved image ratio,
selectivity and frequency response, plus reduced distortion.
Balanced Positive And Negative Power Supply
With Heavy-Duty Components
The power supply unit - backbone of any amplifier — is of
the most elaborate type such as used anywhere in home-use
audio equipment, with balanced dual, polarity supply and
extre large10,000uF capacitors. This results in a tremendous
reserve of power for transient peaks, but also eliminates the
irritating switching noise often encountered in less profes-
sional designs.
Phono Equalizer With Wide Dynamic. Range And
Extremely Close Tolerances
The incoming phono signal from a turntable is equalized
precisely according to the international RIAA standard
playback curve — within 0.3 dB of the ideal, Moreover, the
phono inputs can accept relatively strong signal levels
without distortion (250mV rms), resulting in a wide
dynamic range. This is due to the circuit design with three
direct-coupled amplification stages including a differential
amp in the first stage.
Twin Tone Controls Permit Precise
"Shaping" Of Sound
The overall frequency response curve can be controlled in a
total of seven ways. Twin controls in the bass range permit
variation at 100Hz by +10dB in 2dB steps, and at 50Hz by
+5dB in 2.5dB steps; similarly, the high controls give +10dB
correction in 2dB steps at 10kHz, and again +5dB correc-
tion at 20kHz in 2.5dB steps. All tone controls can be
removed from the circuit (by setting the TONE swtich at
OFF) if desired. High and Low filters are provided for
solving specific noise problems, while the Loudness switch
boosts the very low and high frequencies at soft listening
volumes, giving a more natural sound contour, In one word:
the SX-939 gives you complete mastery over what you
hear.
... Plus A Wealth Of Auxiliary Features
And Circuits
Dolby* inputs and outputs permit confection of an
outboard Dolby noise reduction unit, for example, to
receive Dolby-encoded FM programs.
Two tape monitor circuits allow two tape decks to be used
for recording, playback and tape-to-tape duplicating.
Microphone inputs on the front panel let you use the
SX-939 as a public address amplifier.
Audio muting switch decreases the volume instantly by
20dB without having to turn back the volume control,
Indicator lamps light up in accordance with the functions
used, telling you at a glance what you're hearing and how.
Dimmer switch dims illumination of tuning dial, tuning
meters and indicator lamps, leaving only a softly glowing
light in the dark.
*The word 'Dolby' is a trademark of Dolby Laboratories Inc.
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