YAMAHA CR-1000
¥ 180,000 (around 1974)
Commentary
A top-of-the-line FM receiver developed using Yamaha technology.
The main amplifier circuit uses a pure complimentary service OCL system directly connected to all stages using two differential amplifiers.
The phase correction circuit determined through numerous experiments and computer circuit analysis (CAD method) realizes high stability from the ultra-low band to the ultra-high band with sufficient negative feedback.
In addition, a first stage differential amplifier using a FET with constant current characteristics as a bias circuit and a bias stabilization circuit using a transistor enable stable operation immediately after power supply is turned on.
A large power transformer with good regulation is used for the power circuit.
Power transistors and drive transistors that require a large current are supplied with voltage from a rectifier circuit that uses a large capacity capacitor of 10,000 μ Fx2 and a rectifier diode with a sufficient surge current of 250A. All other circuits are driven by a constant-voltage power supply circuit, enabling stable operation.
Built-in 2-stage protection circuit for power transistor and speaker.
The power transistor protection employs a limiter method that detects when the ASO (safe operating area) is exceeded and limits the input. Even when 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 Yamaha's original circuit method. When the DC voltage at the output terminal exceeds ± 2 v, a relay operates to cut off the signal path to the speakers. This circuit also functions as a power muting circuit to prevent shock noise when the power switch is turned on / off.
The equalizer amplifier section is a direct-coupled amplifier in which a pair of FETs with well-matched characteristics at the first stage and a class A SEPP system with transistors at the output stage.
Because FETs have superior noise characteristics compared to transistors, S/N and distortion factor can be greatly improved. In addition, this circuit has the advantage of greatly improving secondary distortion compared with a single circuit. In addition, the SEPP output stage with low output impedance and a high supply voltage of + 50 V have realized a dynamic margin of 1 kHz for the rated 3 mV and a maximum allowable input of 280 mVrms at a distortion factor of 0.1%.
The equalizer element is composed of a combination of evaporated metal film resistor with ± 1% condenser with ± 1% and ± 2% accuracy, achieving high accuracy.
The input impedance of the Phono1 circuit can be switched to three levels by the switch on the rear panel.
The tone control circuit uses a Yamaha mixing NF and CR type with a 3-stage direct-coupled amplifier.
This system has excellent characteristics in both boost, cut and flat mode, and residual noise is minimized by the careful use of low-noise transistors and noise-conscious design.
The adjustment volume is a Klix/Klukš top-type slide volume. Bass has approximately 3 dB steps and Treble has approximately 2 dB steps. The turnover frequency can be switched to two levels by switching the switch. The center of the turnover switch is in the defeat position, in which the tone circuit operates as a flat amplifier.
A 3-stage direct amplifier is used for the filter circuit.
The cut-off frequency of both the low filter and high filter can be selected by switching to two levels.
Continuous loudness control is used for the loudness circuit.
This circuit is designed to allow the amount of loudness to vary freely, making it possible to make optimum corrections based on the listening environment. The volume can be adjusted from the reference volume level point (FLAT) set in the volume to a point (position 10) that is -20dB lower by adjusting the low and high ranges.
The CR-1000 is designed with an emphasis on the phase characteristics of the FM front-end and the IF stage to minimize the input dependence of the tuner characteristics, which tend to become unstable depending on the strength of the received signal. Thus, the CR-1000 achieves high stability by minimizing the input dependence and reducing the separation and distortion factor at the time of stereo reception due to changes in the input level.
The FM front-end uses a frequency linear 5-row varicon and a low-noise dual-gate MOS FET. The triple-tuned circuit configuration with three tuning circuits realizes excellent intermodulation characteristics and improves various interference rejection characteristics.
In addition, there is almost no tracking error for the frequency scale of the dial scale due to the adoption of the frequency linear type 5-row varicon.
The FM IF stage employs a 7-stage differential amplifier using an IC and a 6-element ceramic filter to obtain good band-pass characteristics such as linear phase characteristics and skirt characteristics.
The FM MPX circuit employs a new method for ultra-low distortion by applying NFB to the average demodulation circuit of the transistor switching method in the same way as the low-frequency circuit. This method does not require the conventional SCA filter, so there is no disturbance in the phase characteristics, and the separation of the high-frequency band is sufficiently ensured, enabling clear reception.
It is also less susceptible to beat interference and SCA band, and the harmonic distortion and intermodulation distortion of the MPX circuit are greatly improved.
An AFC circuit is mounted in order to keep the operation of the tuner section stable.
This AFC circuit uses a unique tuning mechanism that uses electrostatic noise from the human body. The AFC circuit is automatically turned off while the tuning knob is in contact with your hand, so you can select stations with weak radio waves.
The AFC/STATION indicator lights up slightly when you synchronize with the station during channel selection. When you release the knob, the indicator becomes brighter to confirm that the AFC circuit is turned ON.
Uses a signal meter with a large dynamic range.
With conventional signal meters, when the input level exceeds a certain level, the meter drive circuit becomes saturated, and the meter shows the same value, making it difficult to give accurate indication. With the CR-1000, the meter circuit is equipped with an AGC so that the pointer can be moved linearly from a weak electric field to a strong electric field, so that the approximate electric field strength of the input radio wave can be confirmed.
By applying double muting to the input stage and output stage of the FM MPX circuit, noise between stations and shock noise at the time of detuning and tuning are cut. Moreover, the muting level can be controlled from 10 μ V to 50 μ V of the antenna input depending on the slide volume of the front panel, so that the optimum muting effect can be obtained according to the electric field strength of the receiving area.
The FM antenna terminal is equipped with 2 systems of 300 Ω balanced type and 75 Ω unbalanced type.
There is also a connector terminal for coaxial cable that is not affected by external noise.
Equipped with a multi-pass terminal, when the sound quality or separation deteriorates due to direct interference with the reflected radio wave from buildings, etc., the direction in which the multi-pass phenomenon is least can be found while observing the waveform with an oscilloscope.
It can also be easily adjusted by connecting to the Tape PB terminal of the CR-1000.
An IF output terminal for the adapter is installed in preparation for discrete 4-channel broadcasting.
LED is used for each indicator of FM Stereo, AFC/Station and Power.
Built-in dedicated microphone amplifier enables microphone mixing.
It is equipped with two types of tape terminals and two types of speaker terminals.
The preamp section and the main amplifier section can be specified.
It has a unique design that fully uses slide volume and lever switch.
It is also designed with a silver hairline finish front panel and castol-finished cabinet.
Model Rating
| Type | Stereo receiver | ||
| <Audio section> | |||
| Effective output (distortion factor 0.1%) |
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| Dynamic Power | 200W (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 50 kHz | ||
| Frequency characteristic | Main in : 10 Hz to 100 kHz + 0 -1dB Phono (RIAA deviation) : 30 Hz to 15 kHz ± 0.2 dB Aux, Tape PB : 10 Hz to 50 kHz + 0.5 -1dB |
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| Damping factor | 70 (1 kHz, 8 Ω) | ||
| Output terminal | Speaker jacks : A, B Headphone terminal : 4 Ω ~ 16 Ω |
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| Input Sensitivity / Impedance | Phono1, 2 : 3mV/30k Ω, 50k Ω, 100k Ω Mic : 3mV/50k Ω Aux1, 2, Tape PB A, B : 150mV/40k Ω Main in : 775mV/40k Ω |
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| Maximum Allowable Input (1 kHz) | Phono:280mVrms 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) Turnover frequency : 250 Hz, 500 Hz Treble : ± 10 dB (10 kHz) Turnover frequency : 2.5 kHz, 5 kHz |
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| Filter | Low : 20 Hz, 70 Hz (12dB/oct.) High : 6 kHz, 12 kHz (6dB/oct.) |
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| Loudness | Continuous loudness corresponding to an equal loudness curve | ||
| S/N (IHF, A Network) | Main in : 100 dB or more Phono : 80 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 | ||
| Image interference ratio (84 MHz) | 110dB | ||
| IF Interference Ratio (84 MHz) | 110dB | ||
| Spurious interference ratio (84 MHz) | 110dB | ||
| AM suppression ratio | 55dB | ||
| 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 ~ 50 μ V Continuously Variable | ||
| IF out level / impedance | 400mV/1k Ω | ||
| <General> | |||
| Semiconductor used | IC : 2 Transistor : 98 MOS FET : 2 FET : 10 Diode : 56 pcs Zener diode : 5 pcs LED : 3 pcs |
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| AC outlet | Switched : 2 systems, max200W Unswitched-2, max200W |
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| Pwer | 100 VAC, 50Hz/60Hz | ||
| Rated power consumption | 250W | ||
| External dimensions | Width 510x Height 174x Depth 335 mm | ||
| Weight | 19.0kg | ||