YAMAHA CA-V1
¥ 33,000 (around 1976)
Commentary
A pre-main amplifier that pursues circuit, characteristics and functions at an affordable price.
The equalizer circuit is a 2-stage direct-coupled discrete circuit using a low-noise transistor.
The SN ratio is improved by eliminating the use of ICs that do not have much freedom in selecting circuit constants when designing circuits. Transient characteristics are also improved by utilizing data obtained from circuit analysis using computer-aided CAD.
Moreover, by paying attention to the routing and wiring of the print pattern, the SN ratio is prevented from decreasing and shielding wires are eliminated from the input / output circuit.
The tone control circuit is a two stage direct connection type and discrete configuration similar to the equalizer circuit.
The circuit method is the Yamaha CR-NF mixed type. When boosting, the gain of the circuit is increased by the CR in parallel with the NF split resistor. When cutting, the gain is attenuated by the CR inserted at the output side. In this method, the CR time constant of the boost side and the cut side can be made the same, so that the B-type can be used, which is easy to obtain the accuracy of the volume curve, and the characteristics without waviness can be obtained at the midpoint position.
The circuit configuration of the main amplifier section is an input differential-common-emitter ground-pure complimentary service all-stage direct connection OCL circuit in which a current mirror circuit is combined. The power stage and drive stage transistors are selected to have good high-frequency characteristics. By using transistors with good matching PNP and NPN pair characteristics, harmonic distortion and switching distortion can be suppressed.
The meter circuit uses a logarithmic compression circuit with diode negative feedback so that it can read a wide output range from 100 mW to 50W without switching the switch.
The REC OUT selector is equipped to record and output a source other than the one being played back.
If the deck connected to REC OUT is not is not in use, setting it to the REC CUT OFF position will isolate the deck from the signal path, thereby preventing the influence of shield wires and the adverse effect on the amplifier caused by a drop in input impedance when the power supply to the deck is turned off.
Equipped with a loudness circuit, it is possible to improve the characteristics when playing back at a low volume.
A high-precision volume with no ± 2 dB gang error over a wide range from -70dB to 0 is used, and the difference in volume between the left and right channels is very small even at low volume.
A speaker protection circuit by relay is mounted.
When a DC voltage is generated at the output terminal, a relay is used to isolate and protect the speaker. This circuit is also used as a muting circuit to prevent unpleasant clicking noise when the power is turned on.
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Model Rating
| Type | Pre-main amplifier | ||
| Effective power (0.05% strain) | 25W + 25W (8 Ω, double-channel drive, 20 hz to 20 khz) 27W + 27W (8 Ω, double-channel drive, 1 khz) 30W/30W (8 Ω, single-channel drive, 1 kHz) |
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| Dynamic Power (0.05% Strain) | 85W (8 Ω, 1 kHz) | ||
| Total harmonic distortion factor |
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| Power bandwidth | 10 Hz to 50 kHz (IHF, 0.05% THD) | ||
| Damping factor | 50 or More (8 Ω, 1 kHz) | ||
| Load impedance | 4 Ω ~ 16 Ω | ||
| Frequency characteristic | Aux → Rec out : 20 Hz to 20 kHz ± 0.5 dB RIAA deviation : ± 0.5 dB |
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| Channel separation | Aux → SP out : 60 dB or more (8 Ω, 1 kHz, at rated output) | ||
| S/N ratio (IHF A network Closed circuit) |
Phono → SP out : 77 dB Aux → SP out : 100 dB Residual noise : 0.13 mV |
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| Input Sensitivity / Impedance (8 Ω, 1 khz, at rated output) |
Phono : 2.5mV/50k Ω Aux, Tuner : 150mV/50k Ω Tape PB. : 150mV/50k Ω |
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| Phono maximum allowable input | 150 mVrms (1 kHz, 0.05% THD) | ||
| Output Level / Impedance | Tape rec out : 150mV/1k Ω | ||
| Tone control | Bass : ± 10 dB (50 Hz) Treble : ± 9 dB (10 kHz) |
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| Loudness (Vol-30dB) | + 9 dB (50 Hz), + 6.5 dB (10 kHz) | ||
| Other Functions | Output Level Meter (logarithmic scale) Rec out Selector SP protection circuit (voltage detection, relay drive system) |
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| Semiconductor used | Transistor : 34 Diode : 21 Zener diode : 1 unit |
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| AC outlet | Switched : 1 system, 150W Unswitched-2 lines, 200 Wtotal |
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| Power supply voltage | 100 VAC, 50Hz/60Hz | ||
| Rated power consumption | 80W | ||
| External dimensions | Width 435x Height 137x Depth 350 mm | ||
| Weight | 8.5kg |