Technics SU-9070II(70AII)
¥ 120,000 (released in 1977)
Commentary
Stereo control amplifier with newly developed parts.
In the first stage of the equalizer, a newly developed low-noise transistor M47L is used as a differential amplifier. Moreover, a high SN ratio is achieved by operating with a current mirror load that can select an operating current with extremely low distortion while maintaining a high gain.
Uses 6 connected volume that uses CP element (conductive plastic) as a resistor.
Compared with carbon coated resistance, the CP element is a material with superior wear resistance. Moreover, by applying mirror surface finish to the surface, friction with the brush is almost 0. This improves operation feeling and realizes long-term retention with low distortion and low noise.
By inserting the CP element volume before and after the flat amplifier, the S / N ratio in actual use is improved.
A tape monitor is incorporated into the input selector, so that three tape decks can be used by switching the input selector. Also, a recording mode selector is separately installed for recording, so that dubbing is possible regardless of the input selector.
The insertion point on the circuit of the external unit connected to the SU-9070II can be switched by pressing the front panel buttons.
For example, when the UFE (Universal Frequency Equalizer) is connected, the normal switch 1 connects the UFE to the pre-out so that the frequency response of the playback signal can be changed freely. When the switch is pressed, the UFE is connected to the rec out so that the signal can be recorded after the frequency response has been adjusted.
The flat amplifier circuit does not use coupling capacitors for input / output, and adopts a DC configuration that eliminates all capacitors from the NF loop.
The first stage of the circuit is a differential amplifier of constant current drive with dual FET with uniform temperature characteristics. The second stage is a differential amplifier of bipolar transistor and has a two stage differential configuration with excellent DC stability. The second stage consists of a voltage amplifier stage with pure resistance load and a SEPP output stage with Darlington connection.
Furthermore, by driving all stages with a constant voltage power supply, DC drift due to temperature change is suppressed to a level that does not cause any problem.
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Model Rating
| Type | Stereo DC flat preamp |
| Input Sensitivity / Impedance | Phono1, 2 mm : 2.5mV/47k Ω Phono MC : 60 μ V/47 Ω Tuner, Aux : 150mV/47k Ω Tape deck1, 2, 3, Playback : 150mV/47k Ω |
| Total harmonic distortion rate (20 Hz to 20 kHz) | Phono MM:0.003%(VR max at 10V output) 0.003%(VR -30dB at 1V output) Phono MC:0.02%(VR max at 10V output) 0.01%(VR -30dB at 1V output) Tuner, Aux, Tape : 0.003% (VR max at 10 v output) 0.003%(VR -30dB at 1V output) |
| Signal-to-noise ratio (IHF-A) | Phono1, 2 mm : 88 dB Phono MC : 72 dB, -157dBV (input conversion) Tuner, Aux : 106 dB |
| Frequency characteristic | Phono (20 Hz to 20 kHz) : RIAA standard curve ± 0.2 dB Tuner, Aux : 20 Hz to 20 kHz + 0 -0.05 dB 0 Hz to 100 kHz + 0 -1dB |
| Phono maximum allowable input (1 kHz, RMS) | Phono MM:380mV Phono MC:9mV |
| Output Voltage / Impedance | Pre out : 1V/600 Ω (Rating), 20V/600 Ω (Maximum) Tape deck1, 2, 3, Rec out : 150 mv |
| Subsonic Filter | 20 Hz, -12dB/oct (equalizer) |
| Muting | -20dB |
| Pwer | 100 VAC, 50Hz/60Hz |
| Power consumption | 23W |
| External dimensions | Width 450x Height 92x Depth 369 mm |
| Weight | 7.0kg |