Pioneer SX-850 // Vintage / Solid State Receiver / 65wpc

The Pioneer SX-850 is one of those silver-face icons from the peak of the Japanese receiver wars — a mid-line offering that was never meant to be the biggest, but turned out to be one of the most musical. Sixty-five honest watts through a beautifully tuned amplifier section, backed by a phono stage so quiet and RIAA-accurate it still comes up in conversations about the best MM inputs in vintage gear. The sound is warm but never muddy — instruments carry genuine body, voices have real presence and texture, and the FM section is something else entirely, built around a dual-gate MOS FET and four-gang tuning capacitor that pulls stations in with a composure other receivers simply can't match. Over forty years on, the SX-850 remains exactly the kind of receiver that makes you forget you were only going to put on one record.

Production

1976-1978

Condition

9.5/10

Serial No.

WK3623079S

Orig. MSRP

$500

Restoration

• Cleaned all pots and switches
• 2 large and 12 small/medium capacitors replaced
• Replaced the 4 backlight bulbs with LEDs
• Detailed thoroughly

Factory Specs

Power Output 65W per channel, min. RMS into 8Ω, 20Hz–20kHz

Total Harmonic Distortion Less than 0.1%

Intermodulation Distortion Less than 0.1%

Frequency Response 10Hz–50kHz

Damping Factor 25

Speaker Load Impedance 4Ω minimum

Input Sensitivity (Mic) 6.5mV

Input Sensitivity (MM Phono) 2.5mV

Input Sensitivity (DIN / Line) 150mV

Signal to Noise Ratio (MM Phono) 70dB

Signal to Noise Ratio (Line) 90dB

Line Output 150mV

DIN Output 30mV

Pre Out 1V

Tuning Range FM, MW (AM)

FM Sensitivity 1.8µV

FM Capture Ratio 1.0dB

FM Harmonic Distortion (Mono) Less than 0.15%

FM Harmonic Distortion (Stereo) Less than 0.3%

Semiconductors 3 × FET, 3 × IC, 56 × transistors, 36 × diodes

Dimensions 20.73 × 6.81 × 16.20 in (W × H × D)

Weight 42.1 lbs

Documentation

Pioneer SX-850 Owner's Manual
Pioneer SX-850 Service Manual
Pioneer SX-850 Schematics

The History of Pioneer

Pioneer was founded by Nozomu Matsumoto in 1938 in Tokyo as a radio and speaker repair shop. In December 1953 Mr. Nozomu Matsumoto succeeded in developing the first domestic dynamic speaker made of original parts. It was named A-8 and marketed in Japan under the Pioneer brand. It later became the origin of the HiFi ...
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Liner Notes

The Pioneer SX-850 is a high power AM/FM stereo receiver with super-quiet phono equalizer and outstanding FM selectivity/sensitivity. It delivers a continuous power output of 65 watts per channel, min RMS at 8 ohms, from 20 to 20,000 Hertz, with no more than 0.1% total harmonic distortion. But even more importantly, it has the strength and finesse to handle that power with a healthy respect for musicality.

The SX-850 has a super-quiet phono equalizer in a 3-stage direct-coupled design to achieve wide dynamic range and ±0.2dB RIAA equalization accuracy. A FET in the Tone Control section, plus a 2-step frequency turnover switch for Bass and another for Treble, 2-deck monitor/dubbing, 2-system speaker drive, separable pre/main and more, mean further control versatility.

The superb FM/AM section uses a dual-gate MOS FET and a 4-gang variable capacitor to boost sensitivity and selectivity, a PLL IC in the multiplex to improve stereo separation, and a special Integrated Circuit in the AM for still better reception and less noise. It's the Pioneer SX-850 — the one you can trust to keep faith with your musical needs.

Stock No.

9679588360413