Aurex SB-66
¥ 69,800 (around 1980)
Commentary
Pre-main amplifier with clean drive.
It is equipped with Aurex's unique clean drive.
In the Clean Drive method, a distortion component detection code is added to the negative terminal side of the speaker. This detects the distortion component generated in the speaker and feeds it back into the amplifier. Then, the feedback amount is adjusted to cancel the distortion component in the amplifier. This eliminates the distortion caused by the transmission characteristics of the speaker cable and the back electromotive force generated in the speaker, and improves the dynamic characteristics.
Since there is almost no current flow in this detection cord, there is no voltage drop, and the distortion component can be detected at the speaker terminal. Since the cord also detects the impedance with the speaker cable, the voltage at the speaker input terminal becomes equal to the output voltage of the amplifier, and it is a constant voltage drive.
By adopting this clean drive method, the harmonic distortion factor when connected to a speaker is reduced to less than 1 / 10, and intermodulation distortion is also greatly improved. In addition, since the impedance of the amplifier and the speaker cable can be completely cancelled, the impedance seen from the speaker input terminal toward the amplifier is 0, and the damping factor at the speaker input terminal is infinite.
The power amplifier section has a simple DC configuration by eliminating capacitors from the signal path that cause sound quality degradation.
Superf for power transistorsTThe transistor has a transition frequency of 70 a high transition frequency of 70 MHz and can be amplified up to high frequencies. In addition, the switching time is short and the switching distortion is kept to a level that is practically insignificant.
In addition, it has excellent linearity and reduced crossover distortion. Moreover, it is possible to drive with sufficient power by securing sufficient ASO (safe operation region) which is important as a power transistor.
It uses a VX capacitor which is an improved version of the V capacitor used in the SY-88.
In the VX capacitor, the distance between the electrodes is made shorter to realize low impedance and the vibration mode is simplified to minimize the induction of electrical noise.
The equalizer amplifier section is a high-gain equalizer, and both MM and MC cartridges can be used by changing the gain.
The tone control section is configured so that when the tone volume is set to the center, the tone is lost.
It uses a heat sinker that is small but has a large radiator plate area.
In addition to the normal protector, a high-speed protector for the clean drive circuit is mounted.
Even if the distortion detection code for the clean drive is miswired, the protector operates immediately and the clean drive circuit is protected.
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Model Rating
| Type | Pre-main amplifier |
| Power Amplifier Unit | |
| Continuous output | 70W + 70W (8 Ω, 20 Hz to 20 kHz) 72W + 72W (8 Ω, 1 khz) |
| Total harmonic distortion factor | 0.007% (at rated output) |
| Cross modulation distortion factor | 0.007% (at rated output) |
| Frequency characteristic | 5 Hz ~ 100 kHz + 0 -3dB |
| Output Bandwidth (IHF, 0.05% distortion factor) | 5 Hz ~ 100 kHz (8 Ω, both channel drive) |
| Residual noise | 0.5 mv or Less (8 Ω) |
| Speaker impedance | 8 Ω ~ 16 Ω |
| Preamplifier Section | |
| Input Sensitivity / Impedance | Phono MM : 2.5mV/47k Ω Phono MC : 0.25mV/100 Ω Tuner, Aux, Tape play : 150mV/50k Ω |
| Recorded output | 150mV |
| Frequency characteristic | 5 Hz ~ 100 kHz + 0 -3dB |
| Total harmonic distortion factor | 0.007% |
| Tone control | Bass : ± 8 dB (100 Hz) Treble : ± 8 dB (10 kHz) |
| Subsonic filter | 16 Hz, 6dB/oct. |
| Muting | -20dB |
| Equalizer deviation | 20 Hz to 20 kHz ± 0.5 dB |
| Phono maximum allowable input (1 kHz, 0.01% distortion rate) | MM:200mV MC:18mV |
| Signal-to-noise ratio (IHF-A network, short circuit) | Phono MM:88dB Phono MC:73dB Aux:108dB |
| <General> | |
| Semiconductor used | Transistor : 36 IC : 4 Diode : 26 Units FET : 5 pcs |
| Power supply voltage | 100 VAC, 50Hz/60Hz |
| Power consumption | 115W |
| External dimensions | Width 420x Height 151x Depth 399 mm |
| Weight | 9.5kg |
| Attachment | Four clean drive distortion detection cables (3.5m) |