Pioneer TX-620
¥ 28,500 (around 1972)
Commentary
An FM/AM stereo tuner developed in pursuit of supporting performance in order to emphasize sound quality.
The FM front-end is composed of a selected low-noise FET and a single-stage RF amplifier using a frequency linear 3-row varistor.
The IF section has a 5-stage limiter configuration with a high-integration IC dedicated to FM, providing stable limiter characteristics.
In addition, the quadrature method with excellent linearity over a wide band is adopted for detection.
A phase linear ceramic filter (2 elements x2) is used as the selection element. This element has sharp selection characteristics and good phase characteristics in the pass band of IF, so that it can obtain good characteristics with little distortion over a wide range.
In the MPX section, a double-balanced differential demodulation circuit using a high-integration IC is adopted, so stable separation is obtained.
A low-pass filter with sharp cut-off characteristics eliminates carrier leakage.
The AM receiver uses a high-integration dedicated IC with one stage untuned RF amplification.
Since this IC has excellent AGC characteristics, the detection output is kept constant and stable reception is possible even in strong electric field regions.
In addition, the mixer stage is a balanced type with little distortion of local oscillation waveform and excellent spurious characteristics.
Ceramic filter is used for IF stage.
Meters that function as center tuning in FM and signal meters in AM are used.
It is equipped with an MPX noise filter in order to remove the noise which comes in stereo reception in weak electric field.
The rear panel is equipped with independent output level control for FM and AM.
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Model Rating
| Type | AM/FM stereo tuner | ||
| FM Tuner Section | |||
| Circuit system | FETRF 1-stage, 3-series varicon 5-stage limiter, quadrature detection |
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| Practical sensitivity (IHF) | 1.9 μ V | ||
| Capture Ratio (IHF) | 1.5dB | ||
| Execution selectivity (IHF) | 60dB | ||
| S/N | 70dB | ||
| Image Interference Ratio (82 MHz) | 60 dB or more | ||
| IF Interference Ratio (82 MHz) | 90 dB or more | ||
| Spurious interference ratio | 75 dB or more | ||
| AM suppression ratio | 50dB | ||
| Harmonic distortion factor | Mono : not more than 0.2% Stereo : not more than 0.4% |
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| Frequency characteristic |
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| Stereo separation | 1 kHz : 40 dB or more 50 Hz to 10 kHz : 30 dB or more |
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| Carrier leak suppression ratio | 60dB | ||
| Antenna | 300 Ω Balanced Type 75 Ω Unbalanced Type |
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| Accessory circuit | Muting (ON-OFF) MPX Noise Filter (ON-OFF) |
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| <AM Tuner Section> | |||
| Circuit system | Untuned RF1-stage 2-train varicon | ||
| Practical sensitivity (IHF) | Bar antenna : 300 μ V/m 15 μ V |
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| Selectivity | 35dB | ||
| S/N | 50dB | ||
| Image interference ratio | 40 dB or more | ||
| IF interference ratio | 50 dB or more | ||
| Antenna | With Ferrite Bar Antenna | ||
| <General> | |||
| Output Level / Impedance | Fixed : 580mV/2.7k Ω Variable : 60 mv ~ 1.8V/2.5k Ω |
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| Semiconductor used | FET : 1 IC : 3 Transistor : 8 Diode, etc. : 6 pcs |
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| Power supply voltage | 100 VAC, 50Hz/60Hz | ||
| Outlet | Power switch interlock : 1 system | ||
| Rated power consumption | 12W | ||
| External dimensions | Width 415x Height 132x Depth 340 mm | ||
| Weight | 6.7kg | ||