YAMAHA CR-800
¥ 125,000 (around 1974)
Commentary
A receiver that emphasizes sound quality utilizing Yamaha's amplifier technology.
The main amplifier section uses an all-stage direct connection pure complimentary service OCL system circuit with improved stability by the first stage differential amplification.
The power supply section uses a large power transformer with good regulation and a 6,800 μ Fx2 large-capacity capacitor. Together with a separately set constant-voltage power supply that drives all stages except the power stage, the stability of the entire circuit is enhanced.
The protective circuit consists of two stages : power transistor protection and speaker protection.
The power transistor protection circuit employs a limiter method based on ASO detection. Even if the protection circuit is activated due to overload or other reasons, the output only decreases and playback is not interrupted.
The speaker protection circuit uses a relay to shut down the circuit when the voltage at the output terminal exceeds ± 2 v. When the voltage falls within ± 2 v, the circuit automatically returns. This circuit also functions as a power muting and eliminates shock noise when the power switch is turned on or off.
The equalizer circuit consists of a 4-stage direct-coupled circuit. It is designed with attention to noise and has high stability as well as low distortion and high S/N ratio by computer-aided circuit analysis (CAD method).
Moreover, by using carefully selected circuit elements, the RIAA deviation is suppressed to within ± 0.5 dB.
The tone control circuit uses Yamaha's original NF method using a 3-stage direct-coupled amplifier. In addition to low distortion factor, there is no waviness at the middle point of the knob, and flat frequency characteristics can be obtained.
The filter circuit uses the same 3-stage direct-coupled circuit as the tone control circuit.
The low filter is a two step switching type with cut-off frequencies of 70 Hz and 20 Hz. In particular, the 20 Hz position is a subsonic filter. The high filter is a slope with cut-off frequencies of 8 kHz and 6dB/oct. In addition, the high filter can be switched to a high-blend filter that blends the high range of the FM stereo broadcast transmission and eliminates noise components without degrading the frequency characteristics.
It is equipped with a continuous loudness circuit that can compensate for the lowest auditory sense in accordance with the listening environment.
In this circuit, a volume dedicated to loudness can be used to compensate for the actual listener's ear, and the compensation curve is based on an equal-loudness curve between 0 dB and 20 dB.
The FM front-end of the tuner section uses three low-noise dual-gate MOS FETs with excellent high-frequency characteristics for the two RF stages and the mixer stage, thereby greatly improving various interference rejection characteristics including intermodulation characteristics.
In addition, the tuning circuit employs a frequency-linear four string variable capacitor, and the dial scale is equally spaced.
The FM IF stage employs an IC-based 7-stage differential amplifier and a 6-element ceramic filter, realizing excellent band-pass characteristics of linear phase characteristics and skirt curve.
The characteristics of the tuner are easily affected by the strength of the received signal if the input dependence is large.
The CR 800 minimizes this input dependence by focusing on the phase characteristics of the FM front-end and IF stage to minimize stereo separation and distortion due to changes in input level.
The FM MPX circuit uses Yamaha's original switching method in which the NFB is applied to the average demodulation circuit in the same manner as the audio amplifier. This method does not require an SCA filter, so there is no deterioration in phase characteristics, and high frequency separation is ensured.
Auto-touch tuning mechanism is adopted, and stability is improved by applying AFC to the FM front end.
The AFC circuit is automatically canceled while tuning by touching the tuning knob so that it can catch even weak radio waves reliably. In addition, with this Yamaha's original auto-touch tuning mechanism, the AFC/Station indicator lights faintly when it is tuned to the station during tuning, and the indicator lights brightly when it is accurately tuned and released from the knob to indicate that the AFC circuit is operating.
LED is used for 3 indicators on the dial face.
Uses a signal meter with a large dynamic range.
In the conventional signal meter, the meter drive circuit is saturated at an input of 30 dB or more, making it difficult to give an accurate meter indication. In the CR 800, the meter circuit is AGC, so that the pointer can be moved linearly from weak electric field to strong electric field without saturation.
It employs a double FM muting circuit in which muting is applied to the input stage and output stage of the FM MPX circuit, thereby reducing inter-station noise and shock noise at the time of detuning and tuning.
The tuning circuit of the AM tuner section is a triple tune consisting of a 3-row air varicon, ceramic filter and two tuning coils to obtain high stability and excellent selectivity characteristics.
It is also designed to accommodate large power consumption of AM stations, and uses a dedicated AGC circuit that does not distort even at a strong input power of 120dB/m.
Equipped with a microphone mixing circuit with a dedicated amplifier circuit.
Equipped with -20dB audio muting.
The preamp section and main amplifier section can be used separately.
Equipped with two types of speaker terminals.
Equipped with two FM antenna terminals, 300 Ω balanced type and 75 Ω unbalanced type.
Also included is a coaxial cable holder for easy connection.
It is equipped with an IF output terminal for the adapter in order to support discrete 4-channel broadcasting.
Four AC outlets are used.
Exterior finished with front panel of silver hairline and cabinet with Castor Open Pore finish.
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Model Rating
| Type | Stereo receiver | ||
| <Audio section> | |||
| Effective output (distortion factor 0.1%) |
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| Dynamic Power | 130W (IHF, 8 ω) | ||
| Total harmonic distortion rate (20 Hz to 20 kHz) | 0.1% or Less (Effective Output) 0.04% or Less (at 1W output) |
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| Intermodulation distortion factor (70 hz : 7 khz = 4 : 1) | 0.1% or Less (Effective Output) 0.05% or Less (at 1W Output) |
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| Power Bandwidth (IHF, 0.5% distortion factor) | 5 Hz to 70 kHz | ||
| Frequency response (at 1W output) | Main in : 10 Hz to 100 kHz + 2 -1dB Phono (RIAA deviation) : 30 Hz to 15 kHz ± 0.5 dB Aux, Tape PB : 10 Hz to 50 kHz + 0.5 -1dB |
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| Damping factor | 70 (1 kHz, 8 Ω) | ||
| Load impedance | 4 Ω ~ 16 Ω | ||
| Channel separation | 60dB | ||
| Input Sensitivity / Impedance | Phono1, 2 : 3mV/50k Ω Mic : 3mV/50k Ω Aux, Tape PB : 150mV/45k Ω Main in : 775mV/50k Ω |
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| Maximum Allowable Input (1 kHz) | Phono:240mVrms Mic:450mVrms |
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| Output Level / Impedance | Rec out A/B : 150mV/2k Ω Pre out : 775mV/2k Ω |
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| Tone control | Bass : ± 15 dB (50 Hz) Treble : ± 10 dB (10 kHz) |
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| Filter | Low : 20 Hz, 70 Hz (12dB/oct.) High : 8 kHz (6dB/oct), high blend |
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| Loudness | Continuous loudness corresponding to an equal loudness curve | ||
| S/N (IHF, A Network) | Main in : 100 dB or more Phono1, 2 : 75 dB or more Mic : 70 dB or more Aux, Tape PB : 90 dB or more |
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| FM Tuner Section | |||
| Receiving frequency | 76 MHz to 90 MHz | ||
| Practical Sensitivity (IHF, 84 MHz) | 1.7 μ V | ||
| Chinese arrowhead's slope | 50 dB (5 μ V) 60 dB (10 μ V) |
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| Image interference ratio (84 MHz) | 100dB | ||
| IF Interference Ratio (84 MHz) | 100dB | ||
| Spurious interference ratio (84 MHz) | 100dB | ||
| AM suppression ratio | 50dB | ||
| Capture ratio | 1.0dB | ||
| Effective selectivity (IHF) | 80dB | ||
| S/N | 75dB | ||
| Total harmonic distortion rate (400 Hz) | mono:0.15% stereo:0.3% |
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| Stereo Separation (400 Hz) | 45dB | ||
| Frequency characteristic | 50 Hz to 10 kHz ± 0.5 dB | ||
| Subcarrier suppression ratio | 60dB | ||
| Muting signal level | 10 μ V | ||
| IF out level / impedance | 400mV/1k Ω | ||
| <AM Tuner Section> | |||
| Receiving frequency | 525 kHz to 1,605 kHz | ||
| Practical sensitivity | 52dB/m (IHF, bar antenna) | ||
| S/N(80dB/m) | 45dB | ||
| Image interference ratio (1000 kHz) | 70dB | ||
| IF Disturbance Ratio (1000 kHz) | 60dB | ||
| Spurious interference ratio (1000 kHz) | 70dB | ||
| Selectivity (1000 kHz) | 30dB | ||
| Total harmonic distortion factor | 0.8%(80dB/m) | ||
| <General> | |||
| Semiconductor used | IC : 2 Transistor : 98 MOS FET : 3 Diode : 60 Zener diode : 6 pcs LED : 3 pcs |
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| AC outlet | Switched : 2 systems, total 200W Unswitched : 2 systems, total 200W |
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| Rated power consumption | 190W | ||
| External dimensions | Width 474x Height 158x Depth 300 mm | ||
| Weight | 14.0kg | ||