VICTOR/JVC JA-S9
¥ 89,500 (around 1973)
Commentary
This is a pre-main amplifier with not only general characteristics but also a design concept that emphasizes transient response.
All main circuits are designed with an emphasis on transient response to suppress electrical shock by applying a large amount of negative feedback from ultra-high frequency to DC.
As a result, stable operation is realized even for complex musical waveforms in the real world and sharp pulse input such as noise.
The equalizer uses carefully selected low-noise PNP silicon transistors for the first and second stages. The final stage uses high-voltage, low-noise NPN silicon transistors that can withstand up to 250 V. A hybrid C-E feedback 3-stage direct coupling type is used for the final stage. High voltage as high as 85 V is applied.
The power section uses a direct-coupled circuit that does not use a coupling capacitor between the amplifiers.
As a result, a large amount of negative feedback can be applied over a wide range, there is no impedance swell from low to high range, and the damping factor is flat over the whole range.
In addition, stable operation with less low-frequency distortion due to 2-power supply system operation is realized.
7-element SEA is used for tone control.
The SEA system does not change the low and high ranges as in general tone control, but divides the audible band into seven sections, each of which can be changed by ± 12 dB. This allows compensation to match the characteristics of the room and speakers.
The switch can also be used to output the tape out so that the best balance can be achieved before recording.
The protection circuit uses a double-stabilized circuit consisting of an operation amplifier and a zener diode to keep the midpoint potential of the OCL stable.
In the event of transistor breakdown or other accident, the detection circuit immediately operates to protect the speakers.
In addition, the shock sound generated when the power is turned ON/OFF is also prevented by the relay circuit.
It has a built-in pink noise generator as an attachment mechanism and can be used for multi-amplifier level check and speaker phase check.
Equipped with low-cut and high-cut filters.
It uses a 4-channel master volume with a mutual deviation of less than 1 dB, which can be used in a 4-channel system, and has input / output terminals for that purpose.
You can also use 4 channels of loudness control and muting circuits.
It is equipped with mechanisms such as alternating dubbing switch of 2 series tapes, switching and simultaneous connection of 2 series speakers, 3-stage switching of cartridge load, input level adjustment of Phono1/AUX1, premain separation terminal, etc.
The wood case was sold separately.
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Model Rating
| Type | Integrated stereo pre-main amplifier |
| Circuit system | Power Amplifier : All Stages Directly Connected Pure complimentary service OCL |
| Power Amplifier Unit | |
| Music Power (IHF) | 4 Ω : 220W (110W + 110W) 8 Ω : 170W (85W + 85W, 1 kHz) |
| Effective output (8 Ω, 1 kHz) | Double-channel drive : 120W (60W + 60W) Single-channel Drive : 100W (50W + 50W) |
| 20 Hz ~ 20 kHz (Both Channel Drive) | 100W (50W + 50W, 1 kHz) |
| Harmonic distortion factor (at effective output) | 0.05%(50W) |
| Intermodulation distortion factor (at 1W output) | 0.4% |
| Power band wiz | 10 Hz ~ 30 kHz (50W, both channels, 8 Ω, THD 0.25%) |
| Frequency response (at 1W output) | 5 hz to 450 khz -3dB |
| Damping factor | 50 (8 Ω Load) |
| Load impedance | 4 Ω ~ 16 Ω |
| Input sensitivity | 1V |
| Preamplifier Section | |
| Frequency characteristic | 20 Hz to 50 kHz ± 0.5 dB |
| Input Sensitivity / Impedance | Phono : 2.5mV/47k Ω AUX, Tape Play : 200mV/100k Ω |
| S/N(IHF/RMS) | Phono:91dB/63dB AUX:101dB/86dB |
| Equalizer characteristics (RIAA deviation) | ± 0.5 dB |
| Phono maximum allowable input | 840mV(P-P) 300mV(RMS) |
| Cartridge load switching | 33k Ω, 47k Ω, 100k Ω |
| Recording output level | PIN:180mV DIN:30mV |
| Tone control | SEA center frequency : 40 Hz, 150 Hz, 400 Hz, 1 kHz, 2.4 kHz, 6 kHz, 15 kHz SEA variable range : + / - 12 dB |
| Filter | Subsonic : 18 Hz, 12dB/oct. High : 9 kHz, -12dB/oct. |
| Muting | -20dB |
| Loudness (at Volume -30dB) | 50 Hz + 11 dB, 1 kHz + 1.5 dB, 10 kHz + 4 dB |
| <General> | |
| Semiconductor used | Transistor : 39 Diode, etc. : 16 pcs |
| Pwer | 100 VAC, 50Hz/60Hz |
| Power consumption | 135W |
| External dimensions | Width 420x Height 138x Depth 333 mm |
| Weight | 11.5kg |
| Sold Separately | Wood Case WD-1 (¥ 3,400) |