Audio Database

SC - Λ 90F
Commentary

This is a stereo power amplifier developed for the digital audio age based on the technology developed in the SC-Λ 99 and SY-Λ 88 II.

Equipped with newly developed complimentary service power MOS FET.
This power MOS FET (2SK405, 2SJ115) developed by Aurex employs a double diffusion structure called π -MOS, which realizes high voltage resistance, high gain, and high speed.
In addition, it realizes high power by keeping the on-resistance low at the same time. Moreover, conventional driver circuits can be used as they are, and parallel use is easy.

The newly developed power MOS FET is connected in parallel, the first stage dual FET cascode connection, the second stage dual transistor differential cascode connection, and the Darlington connection at the current mirror voltage amplification stage for driving.

The input stage employs 2SK270A, a low-noise dual FET used in the SY - Λ 88 II and SC - Λ 99. In addition, a super Λ power supply, which is well known for its low-noise and low-impedance over a wide band, is introduced to suppress noise in the power supply.
In addition, a low-noise driver circuit is designed to reduce internal resistance and prevent thermal noise by allowing sufficient current to flow through the semiconductor element, resulting in an excellent S / N ratio.

In order to promote low noise and low impedance between the AC power supply and the amplifier, a super Λ power supply is used in the power supply section up to the pre-driver stage to improve sound quality.
A large 410 VA toroidal transformer is used for the power transformer. The secondary winding consists of three separate power sources for power amplification, voltage amplification (driver circuit), protection circuit and indicator, reducing mutual interference.
In order to reduce the impedance, the power switch has a large capacity and a rectifier is used in parallel. The rectifier is a high-speed type and the terminal is covered with silver cladding.
A high-quality large-capacity large-capacity electrolytic capacitor developed in the SC - Λ 99 is used in the circuit for the power amplifier stage. In addition, a newly developed electrolytic capacitor is used in the Super Λ power supply for the driver amplifier stage. Each electrolytic capacitor is connected in parallel with a u Λ -II type Λ capacitor, a copper foil styrene capacitor, a V-capacitor, etc., so that low impedance, reduction of contact between dissimilar metals, and prevention of vibration are greatly improved.

Unlike general DC amplifiers, this DC amplifier is designed as a servo-less DC amplifier to prevent degradation of sound quality caused by DC servo circuits containing active elements.
As a result, the feedback circuit that affects sound quality is simplified, and excellent music playback is possible even at high output.

The basic signal circuit has a very simple structure, and high-reliability carbon resistance called RM resistance is used in parallel for the resistance of the NFB loop and each signal system. By making the resistance different from each resistance value, the frequency of noise is dispersed, coloring caused by the noise of resistance is eliminated, and the flatness of audibility is taken into consideration.
In addition, where non-linear components of the transistor are generated, capacitors made of copper foil styrene capacitors wrapped with butyl rubber to prevent vibration are used to suppress the noise of the capacitors.

As solid capacitors for the signal and power supply systems, we have adopted copper foil styrene capacitors, u Λ -II type Λ capacitors, GU capacitors, etc., which have the same reputation as Λ 99. In addition to low impedance, we greatly promote reduction of contact between dissimilar metals and vibration prevention.
In addition, a special manufacturing method has been used to reduce resonance over a wide band and to realize characteristics with good energy balance.

As the source resistance of the power MOS FET at the output stage, we have adopted a Λ resistor made of copper, which was also used for Λ 99. As a result, all the paths through which a large current flows are unified with elements using copper, and a Λ loop circuit that does not mix dissimilar metals is achieved.

Equipped with a large peak power meter, monitoring is possible without range switching.
The brightness of the meter can be changed in 2 levels.

Equipped with two input terminals, direct and variable.
The variable terminal allows volume control with the front volume control switch, and the volume position can be confirmed by the 5-point LED on the front panel.
The direct input jack directly connects to the first stage of the amplifier without passing through the input volume.

It is equipped with Aurex's unique clean drive circuit.
A third cord connected to the negative terminal of the speaker detects the distortion component caused by the nonlinear component of the back electromotive force and feeds it back into the amplifier to cancel the distortion. This reduces harmonic distortion to less than 1/10, greatly reduces intermodulation distortion, provides flat frequency characteristics, makes the impedance of the speaker cord 0, and has an infinite damping factor.
The Clean Drive terminal is designed to be connected to the negative terminal side of the speaker for maximum power. In case of emergency, it is equipped with a low-speed protection circuit to protect the set from incorrect connection.

In addition to the conventional protection circuit that protects the amplifier when DC voltage leaks into the speaker output terminal or the speaker is short-circuited, a temperature protection circuit is also installed to protect the set from abnormal high temperature inside the set and prevent thermal runaway.

Model Rating
Type Stereo power amplifier
Amplifier Unit
Rated Output (20 Hz ~ 20 kHz) 100W + 100W (8 Ω)
Total harmonic distortion rate (20 Hz to 20 kHz) 0.007% (8 Ω at rated output)
Intermodulation distortion factor (50 hz : 7 khz = 4 : 1) 0.007% (at rated output)
Frequency characteristic DC ~ 100 kHz + 0 -1dB
Output Bandwidth (8 ω, 0.05% distortion) 5 hz to 100 khz -3dB
Input Sensitivity / Impedance 1V/50k Ω
Residual noise (input short) 70 μ V (8 Ω)
Signal-to-noise ratio (IHF, A-network) -126dB (input conversion)
Damping factor 150
Speaker impedance A, B : 4 Ω ~ 16 Ω
A + B : 8 Ω ~ 16 Ω
Meter Section
Meter indication range 1 mW ~ 200W (8 Ω)
-50dB to + 3 dB
Indication accuracy -50dB or more : 20 Hz to 20 kHz ± 2 dB
-50dB or less : 20 Hz to 20 kHz ± 3 dB
<General>
Power supply voltage 100 VAC, 50Hz/60Hz
Power consumption 320W
External dimensions Width 420x Height 158x Depth 385 mm
Weight 15kg