AM/FM Stereo Receiver
The power amplifier of the Pioneer SX-3000 is configured as a differential amplifier with a diode current mirror for the first stage and a 2-stage Darlington connection pure complementary OCL circuit. The power supply adopts a dual positive/negative supply system with two power transformers and features a configuration with ample power thanks to the 8,200 uF electrolytic capacitors. The result of these features is a continuous power output of 35 watts per channel minimum at 8 ohms from 20 Hertz to 20,000 Hertz, with no more than 0.03 % total harmonic distortion.
The equalizer circuit is configured as a 3-stage direct-coupled E-E feedback circuit combining PNP, NPN and PNP transistors and the impedance of the RIAA elements is reduced to give a signal-to-noise ratio of 84 dB (IHF A network, short-circuit) and a maximum rated input of 200mV (1kHz, THD of 0.03%) for a high level of fidelity to the original sound.
The SX-3000 tone control circuit employs a power tone circuit with a built-in power amplifier negative feedback circuit and this enables the power amplifier's distortion to be suppressed to a low level. It is also a centre defeat type of tone control and so when it is set to its centre position, a perfect flat frequency response is obtained.
The FM front end is composed of an RF amplifier employing a dual gate MOS FET and a local oscillator with a built-in servo lock circuit. The dual gate MOS FET has a high input impedance and does not affect the tuning circuitry and so this permits a high selectivity and effective suppression of image interference and spurious interference.
The IF amplifier is provided with a 2-stage ceramic filter with superb selectivity and a buffer amplifier is inserted between the stages to enhance both the selectivity and the sensitivity and to produce a sound with the minimum interference and noise.
The servo lock circuit functions to compensate for any shifts in the tuning accuracy caused by changes in the temperature or humidity or other environmental deviations. Any tuning shifts are detected from the output signal of the detector, the local oscillation frequency of the front end is controlled and stable reception is maintained. Another outstanding feature of this circuit is the delay circuit which prevents the broadcasting stations in the vicinity of the tuning pointer from being pulled in during the tuning operation. This paves the way for accurate and precise tuning and for best tuning results.
A new tuning display in the form of a two-role FM tuning and AM signal tuning indicator employing three LEDs (light-emitting diodes) is features in this receiver. When an FM station is being tuned in, the LED on the extreme left or right lights up to indicate that the broadcasting station is at hand. When the station is fully tuned, the centre LED lights up to indicate the optimum reception point. This LED threesome is known as the centre tuning indicator.
When tuning in an AM station, the left-hand LED will light up first and the strength of the signals is indicated by the intensity of that LED. Stronger signals cause the other LEDs to light up in succession. An AM station can therefore be finely tuned by observing the degree of brightness of the LEDs and this helps enhance the precision of the tuning operation.
The Pioneer SX-3000 is a mini component designed with priority given to handling ease. Features include a wide-spread dial scale and handsome hair-line finished front panel, function and speaker switches with LED indicators, larger-than-before controls and a tuning knob for easy operation, and a truly compact size for added convenience.
Tuning range: FM, MW
Power output: 35 watts per channel into 8Ω (stereo)
Frequency response: 10Hz to 100kHz
Total harmonic distortion: 0.03%
Damping factor: 40
Input sensitivity: 2.5mV (MM), 150mV (line)
Signal to noise ratio: 78dB (MM), 95dB (line)
Output: 150mV (line)
Semiconductors: 2 x FET, 4 x IC, 51 x transistors, 36 x diodes
Dimensions: 380 x 84 x 338mm
Accessories: FM T-type antenna
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