Pioneer TX-8900II
¥ 65,800 (released in 1976)
Commentary
An FM/AM tuner that focuses on improving sound quality such as low distortion rate, high signal-to-noise ratio, and wide-band as well as improving reception performance.
The FM front-end uses an RF2-stage amplifier circuit consisting of a 5-series varicon and three dual-gate MOS FETs with a low noise figure, providing high sensitivity and high interference rejection capability.
In addition, in order to emphasize sound quality, we focus on the phase distortion of the front end and improve the coupling between stages of the front end by precise adjustment to improve the phase characteristics.
The IF part uses 2-stage switching of wide selectivity / narrow selectivity.
The narrow band has a narrow band with an effective selectivity of 85 dB with five carefully selected 2-element ceramic filters. In addition, the sound quality has been improved by using an ultra-wide-band linear detector with an extremely linear bandwidth of ± 6 MHz.
In addition to using this ultrawide-band linear detector for the wide-band, we have combined a 4-pole phase linear filter with a newly developed surface acoustic wave (SAW) filter in order to obtain even more thorough low distortion.
In addition, a newly developed dedicated IC (PA-3001) is used for control signals for meter indication and muting to improve reliability.
In the MPX section, the 19 kHz pilot signal is canceled by the pilot signal auto-cancel circuit using the newly developed MPX PLL IC (PA-1001) to suppress the high-frequency degradation caused by the filter.
A newly developed dedicated IC (PA 1002) is used for the audio amplifier and muting circuit.
In the audio amplifier section, SN ratio and distortion factor are improved by using differential amplification and de-emphasis circuit with NFB operation. In the muting circuit, low-cut filter with cut-off frequency of 10-odd Hz, which was conventionally used for eliminating pop sound, is lowered to 8 Hz by electronic switching with fast response in the IC, and low-band characteristics are extended.
The muting level can be switched to 2 levels.
The power supply section uses a newly developed exclusive IC (PA-2002) with a load current of 300 mA and ripple compression ratio of 80 dB or more to improve the S / N ratio. It also has a highly reliable configuration with built-in overcurrent and overvoltage protection circuits inside the IC.
Equipped with a change-over switch that sends out the multipath component to the tuner output.
This makes it possible to find the direction of the antenna with less multipath components while listening to the sound from the speaker without an oscilloscope.
There is also a separate multi-pass terminal for the oscilloscope.
Equipped with a Rec level check switch, a highly stable circuit composed of ICs enables the tuner output to send a 440 Hz signal sound at the same level as when FM50% is modulated at 1.6 second intervals.
The AM tuner section consists of a 3-row varicon and IC.
Four slide-type memory markers are mounted on the lower part of the dial face.
Equipped with an MPX noise filter.
There are two types of output terminals, fixed and variable.
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Model Rating
| Type | AM/FM stereo tuner | |||||||||
| FM Tuner Section | ||||||||||
| Circuit system | MOS FET RF2-stage 5-row varicon with IF BAND switching Ultra-wideband detector Pilot signal auto-canceler, NFB system MPX |
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| Practical sensitivity | Mono : 1.7 μ V/9.8 dBf (new IHF) | |||||||||
| S/N50dB sensitivity | Mono : 2.8 μ V/14.0 dBf (new IHF) Stereo : 35 μ V/36.1 dBf (new IHF) |
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| S/N | mono:82dB stereo:77dB |
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| Harmonic distortion factor |
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| Capture ratio | wide:0.8dB narrow:2.0dB |
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| Effective selectivity | wide:35dB(400kHz) narrow:85dB(400kHz) 65dB(300kHz) |
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| Stereo separation | wide:50dB(1kHz) 35 dB (50 Hz to 15 kHz) narrow:45dB(1kHz) 30 dB (50 Hz to 15 kHz) |
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| Frequency characteristic | 20 Hz to 10 kHz ± 0.2 dB 20 Hz to 15 kHz + 0. 2-0. 5 dB |
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| Image interference ratio | 120dB | |||||||||
| IF interference ratio | 115dB | |||||||||
| Spurious interference ratio | 110dB | |||||||||
| AM suppression ratio | 65dB | |||||||||
| Subcarrier ratio | 77dB | |||||||||
| Muting action level | 5 μ V/19.2 dBf 28 μ V/34.1 dBf |
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| Antenna | 300 Ω Balanced Type, 75 Ω Unbalanced Type | |||||||||
| <AM Tuner Section> | ||||||||||
| Circuit system | Tunable RF1-stage 3-train varicon | |||||||||
| Practical sensitivity | 300 μ V/m (bar antenna) 15 μ V (external antenna) |
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| Selectivity | 30dB | |||||||||
| S/N | 55dB | |||||||||
| Image interference ratio | 70dB | |||||||||
| IF interference ratio | 65dB | |||||||||
| <General> | ||||||||||
| Output Level / Impedance |
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| Semiconductor used | Transistor : 12 FET : 5 pcs IC : 15 Diode, etc. : 21 |
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| AC outlet | Power switch not linked : 1 system | |||||||||
| Power supply voltage | 100 VAC, 50Hz/60Hz | |||||||||
| Power consumption (Electrical Appliance and Material Control Law) | 24W | |||||||||
| External dimensions | Width 420x Height 150x Depth 392 mm | |||||||||
| Weight | 9.4kg | |||||||||