Pioneer SX-757
¥ 78,500 (around 1975)
Commentary
This is a stereo receiver that pursues performance equivalent to the high class separate type.
The power amplifier section uses a pure complimentary service OCL circuit with 1 stage differential amplifier using ± 2 power supply system.
This circuit takes into consideration not only high power but also low distortion factor by using dual transistors with uniform characteristics in the differential section.
A 15,000 μ Fx2 large-capacity capacitor is used for the power supply.
The equalizer amplifier section uses a high-voltage low-noise IC with one stage differential amplification using ± 2 power supplies. The RIAA deviation is kept within ± 0.2 dB by using carefully selected elements such as metal film resistors with an error of less than 1% and styrene capacitors with an error of less than 2%.
In addition, high voltages of + 21 v and -19V are applied to the IC used, and the maximum allowable input is 200 mv, which corresponds well to the dynamic range of the record.
The control section uses the same low-noise IC for the tone stage as the equalizer section to obtain low distortion and high output.
The tone control uses a CR type circuit, and both Bass and Treble are 11-step variable type. Since it comes with a Klix/Klukš top, it can be accurately returned to its original position even if you turn the knob.
A tone circuit OFF switch is also provided to make the tone flat, in which case the tone circuit is bypassed.
Attenuator type is used for the main volume.
This is a 32-step dB display, and the amount of sound attenuation can be read accurately. Moreover, the left / right linkage error is within 0.5 dB over the range of 0 to -70dB, so there is no worry that the left / right balance will change according to the volume change.
Two tape I/O circuits are mounted.
Equipped with a low-cut filter.
With the built-in loudness contour, you can enjoy powerful sound quality even when playing at a small volume.
A microphone jack is mounted on the front panel.
If you insert the microphone jack when the function switch is in the Aux/Mic position, the Mic has priority and the Aux is disconnected.
The front-end of the tuner consists of a high-frequency amplifier stage with a dual-gate MOS-FET in the first stage and a four series varicon. By adopting an FET with low noise coefficient, a practical sensitivity of 1.9 μ V is obtained, as well as interference rejection capability and excellent characteristics.
The IF section is based on a dedicated high-integration IC, combined with two differential ICs and three 2-element ceramic filters, and uses a circuit configuration with a 5-stage limiter.
In addition, this circuit adopts the latest design in which a ratio detection circuit is installed in addition to the IC used at that time, making the distortion factor and SN ratio more advantageous. In addition, the width of the tuning point is expanded by a design that allows the impedance matching between the three filters to be discretionary, and it has excellent tuning characteristics that do not increase the distortion even if there is a slight tuning deviation.
The MPX section uses a newly developed PLL circuit using a dedicated IC.
Equipped with an ON/OFF capable FM muting circuit, unpleasant inter-station noise can be eliminated.
This circuit has L/R-independent design and allows FM muting without clicking sound.
The AM tuner section uses a dedicated high-integration IC and consists of a high-frequency amplifier 1-stage and a two stage varicon.
It uses a 2-meter system similar to the stand-alone tuner.
Uses a tuning mechanism with a large flywheel.
All input / output terminals and circuits are integrated on a single large board, and input shielding wires are eliminated to improve sound quality.
The height of the panel surface of the SX-7A is the same as that of the CT-7A cassette deck, so you can enjoy a unified design when used side by side with the SX 757.
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Model Rating
| Type | Stereo receiver |
| Amplifier Unit | |
| Circuit system | Pure complimentary service OCL |
| Effective output (20 Hz to 20 kHz, both channels driven) | 55W + 55W (4 Ω) 50W + 50W (8 Ω) |
| Harmonic distortion factor (20 Hz to 20 kHz) | 0.1% (Effective Output) 0.03% (8 Ω at 25W output) 0.05% (8 Ω at 1W output) |
| Intermodulation distortion factor (50 hz : 7 khz = 4 : 1) | 0.1% (Effective Output) 0.03% (8 Ω at 25W output) 0.03% (8 Ω at 1W output) |
| Output Bandwidth (IHF, both channel drives) | 5 Hz ~ 40 kHz (Distortion Factor 0.1%) |
| Output terminal | Speaker : A/B (4 ~ 16 Ω), A + B (8 ~ 16 Ω) Headset : 4-16 Ω |
| Damping factor | 30 (20 Hz ~ 20 kHz, 8 Ω) |
| Input Sensitivity / Impedance | Phono : 2.5mV/50k Ω Mic : 5mV/50k Ω Tuner, Aux, Tape play1/2/2 (DIN) : 150mV/50k Ω |
| Phono maximum allowable input (harmonic distortion rate 0.1%) | 200mV(1kHz) |
| Output Level / Impedance | Tape rec1/2:150mV Tape rec2 (DIN) : 30mV/80k Ω |
| Frequency characteristic | Phono (RIAA deviation) : 30 Hz to 15 kHz ± 0.2 dB Tuner, Aux, Tape play : 10 hz to 50 khz + 0 -1dB |
| Tone control | Bass : + 8 dB, -7dB (100 Hz) Treble:+9dB -7dB(10kHz) |
| Filter | 30Hz(6dB/oct) |
| Loudness contour (Volume-40dB) | + 6 dB (100 Hz), + 3 dB (10 kHz) |
| S/N ratio (IHF, A-Network, short circuit) | Phono:70dB Tuner, Aux, Tape play : 90 dB |
| FM Tuner Section | |
| Practical sensitivity | S/N 50dB Mono : 4 μ V Stereo : 50 μ V IHF Mono : 1.9 μ V |
| S/N | mono:78dB stereo:75dB |
| Harmonic distortion factor | mono:0.1%(100Hz) 0.1%(1kHz) 0.2%(10kHz) stereo:0.25%(100Hz) 0.25%(1kHz) 0.5%(10kHz) |
| Capture ratio | 1.2dB |
| Effective selectivity | 80dB(400kHz) |
| Frequency characteristic | 50 Hz to 10 kHz + 0. 2-0. 5 dB 20 Hz to 15 kHz + 0.2 -2.0 dB |
| Separation | 40dB(1kHz) 35 dB (50 Hz to 10 kHz) |
| Image interference ratio | 90dB |
| IF interference ratio | 90dB |
| Spurious interference ratio | 90dB |
| AM suppression ratio | 55dB |
| Carrier leak suppression ratio | 65dB |
| Stereo switching level (muting operation level) | 2.2 μ V |
| Antenna | 300 Ω Balanced Type 75 Ω Unbalanced Type |
| <AM Tuner Section> | |
| Practical sensitivity | 300 μ V/m (bar antenna) 15 μ V (IHF) |
| Selectivity | 35dB |
| Signal-to-noise ratio | 50dB |
| Image interference ratio | 40dB |
| IF interference ratio | 70dB |
| <General> | |
| Semiconductor used | FET : 3 IC : 9 Transistor : 35 Diode, etc. : 37 pcs |
| Power supply voltage | 100 VAC, 50Hz/60Hz |
| AC outlet | Power switch interlock : 1 system Power switch not linked : 1 system |
| Power consumption | 140W (Electrical Appliance and Material Control Law) 330W maximum |
| External dimensions | Width 455x Height 160x Depth 369 mm |
| Weight | 14.3kg |
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