Pioneer TX-8900
¥ 65,000 (around 1975)
Commentary
AM/FM stereo tuner with Rec level check function.
The front-end is equipped with a frequency-linear 5-row varicon and a low-noise dual-gate MOS FET (RFAmp. x2, Mixerx1). The sensitivity is improved by using a FET with a low noise figure and by increasing the gain of the next stage IF amplifier.
A buffer circuit is provided in the local oscillator circuit to improve stability, and there is no pull-in phenomenon even when there is an adjacent station with a strong electric field, and drift is suppressed.
The IF section consists of six 2-element ceramic filters with excellent phase characteristics and seven differential amplifier ICs. It is equipped with an 8-stage limiter, and the IF detection circuit of the control system is separated from the IF amplifier to achieve stable operation.
The detector of the IF section employs an ultra-wideband linear detector identical to that used in the TX 9900.
Since this detector has a bandwidth of 6 MHz and high detection efficiency, it is advantageous in terms of distortion reduction and signal-to-noise ratio, contributing to improved sound quality.
The MPX section uses a PLL method. The PLL does not degrade the separation characteristics even if there are changes in temperature and other factors, so it has stable characteristics.
It also incorporates a low-pass filter with sharp characteristics to prevent beat interference and intermodulation during FM recording.
It is equipped with a recording level check function. When this function is activated, a 440 Hz signal sound will appear on the sy power of the tuner at the same level as when FM50% is modulated for approximately 1.3 seconds. If you adjust the level so that this signal is located between -2 and 0 dB on the deck meter, the broadcast level setting will be almost correct.
In addition, this signal sound can be used for adjusting the phase of the speakers and balance check the left and right volume.
Equipped with a 2-step switching type muting circuit. This circuit also has a power supply muting circuit, so there is no noise when the power supply is turned on/off.
The AM section uses a 3-row frequency number line type varicon with dedicated ICs and ceramic filters.
It is equipped with an MPX noise filter to eliminate high-frequency noise that tends to occur when receiving stereo signals in weak electric fields.
It has two fixed and variable output terminals, multi-path terminals and four chMPX terminals.
Model Rating
Type | AM/FM stereo tuner | ||||
FM Tuner Section | |||||
Circuit system | MOSFET RF2-stage, 5-series variable capacitor, 8-stage limiter Ultra wideband detector, PLL MPX |
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Practical sensitivity | Mono : 2.5 μ V (S/N50dB) / 1.5 μ V (IHF) Stereo : 35 μ V (S/N50dB) |
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S/N | mono:80dB stereo:75dB |
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Harmonic distortion factor |
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Capture ratio | 1.0dB | ||||
Effective selectivity | 85dB(400kHz) 55dB(300kHz) |
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Separation | 40 dB or More (1 kHz) 35 dB or More (50 Hz to 10 kHz) |
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Frequency characteristic | 50 Hz to 10 kHz + 0. 2-0. 5 dB 20 Hz to 15 kHz + 0.2 -1.5 dB |
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Image interference ratio | 110 dB or more | ||||
IF interference ratio | 110 dB or more | ||||
Spurious interference ratio | 110 dB or more | ||||
AM suppression ratio | 55dB | ||||
Carrier leak suppression ratio | 65dB | ||||
Muting action level | 5 μ V/22 μ V | ||||
Antenna | 300 Ω Balanced Type, 75 Ω Unbalanced Type | ||||
<AM Tuner Section> | |||||
Circuit system | Tuned RF1-stage, 3-series varicon | ||||
Practical sensitivity | 300 μ V/m (bar antenna) 15 μ V (IHF) |
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Selectivity | 40dB | ||||
S/N | 50dB | ||||
Image interference ratio | 65 dB or more | ||||
IF interference ratio | 85 dB or more | ||||
<General> | |||||
Output Level / Impedance | Fixed : 650mV/5k Ω Variable : 70 mv ~ 2V/3.5k Ω 4 ch MPX : 400mV/2.5k Ω |
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Semiconductor used | Transistor : 34 FET : 3 IC : 11 Diode, etc. : 23 pcs |
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AC outlet | Power switch not linked : 1 system | ||||
Power supply voltage | 100 VAC, 50Hz/60Hz | ||||
Power consumption | 18W (rated) | ||||
External dimensions | Width 420x Height 150x Depth 365 mm | ||||
Weight | 9.1kg |