Aurex SB-Λ 70

Commentary

Pre-main amplifier with clean drive and high sound quality parts.

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.

We have adopted the copper-evaporated metallized polyester film capacitor "Λ capacitor" used in SY-Λ 88. This capacitor realizes a balanced sound with less distortion by simplifying vibration mode and reducing impedance.

It uses an improved VX capacitor based on the V capacitor used in the SY-88.
This condenser achieves high sound quality by reducing electrical noise through low impedance and simplification of vibration mode.

A newly developed electrolytic capacitor (10,000 μ F, 63 WV) is used for the power supply.
The sound quality is improved by carefully examining the materials used, using paste with fast response speed, low-magnification electrode foil by special etching, formation of chemical film by special method, and structure to improve sound quality.

The power transistor has a transition frequency of 70 MHz or more._TTransistors are used to enable stable amplification up to high frequencies, and dual transistors with excellent temperature characteristics are used in the first stage to form a DC power amplifier configuration.

Both A and B speakers have clean drive circuits.

The tone control section uses a self-defeat system in which the volume automatically loses tone at the center click position.

The equalizer amplifier section is designed to have high gain and can be used for both MM and MC by changing the gain.

Gold plated terminal is used for phono terminal.

Equipped with a dedicated high-speed protector for the clean drive circuit, it protects the circuit even if the distortion detection cord is miswired.

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)