Audio Database

SC-77
Commentary

This monaural power amplifier has a thin structure and pursues the appeal of monaural amplifiers.

All stages are directly connected and pure complimentary service OCL circuit of 3-stage Darlington connection including 2-stage differential with cascode connection at the first stage.
The circuit up to the driver stage is supplied with power by a low impedance constant voltage circuit, which improves the S / N ratio and distortion factor at small output as well as stabilizing it.
In addition, a non-inductive metallized polyester film condenser is used for the input part, and the deterioration of sound quality is suppressed by eliminating the electrolytic condenser.

The power supply section is equipped with a large toroidal transformer and two low-magnification 11,000 μ F electrolytic capacitors.
The low-magnification capacitor has a structure in which the area ratio magnification of etching is controlled to 10 to 12 times. Although it has a large capacity, the current density increases because the current path is thick, and it has succeeded in reducing the DC impedance of the electrode. In addition, the AC impedance is also reduced by using a multi-terminal structure in which the electrode is discharged from several places of the anode foil.
The power supply for class A circuit and class B circuit is divided, and consideration is given to prevent the waveform of class B circuit from jumping into class A circuit in terms of structure layout.

A pure copper ground line and a 70 μ m thick copper PC board are used to reduce the impedance of the signal system.

It is equipped with an input gain change-over switch which changes the NF amount of the first stage, and sensitivity can be improved by about 10 dB.
This can be used for direct drive with the equalizer output of a preamplifier.

Equipped with a subsonic filter.

Equipped with attenuator type level control.

Dedicated output terminal for level meter detection is provided.

Attached is a data sheet measured by computer (CADIS).

There was a carrying handle as an option sold separately.

Model Rating
Type Monaural power amplifier
Circuit system First Stage Cascode / Differential Second Stage / Third Stage Darlington
Pure complimentary service OCL Parallel Push-Pull directly connected to all stages
Continuous Output (20 Hz ~ 20 kHz, Distortion 0.05%) 120W (8 Ω)
170W (4 Ω)
Harmonic distortion factor
20 Hz to 20 kHz :


1kHz:
50kHz:
100kHz:
0.05% (Continuous Output)
0.04% at 60W output
0.05% (at 1W output)
0.002% at 60W output
0.02% (at 60W output)
0.08% at 60W output
Intermodulation distortion factor (50 hz : 7 khz = 4 : 1) 0.08% (at continuous output)
0.03% (at 1W output)
Output Bandwidth (IHF) 5 Hz to 100 kHz (0.1% Distortion Factor)
Frequency characteristic 5 Hz ~ 100 kHz + 0 -1dB at 1W Output
Input Sensitivity / Impedance 1.6V/50k Ω
* Sensitivity can be increased by 10 db by switching the switch.
Damping factor 50 (8 Ω)
Signal-to-noise ratio (IHF-A network) 115dB
Residual noise 0.3mV
Subsonic filter 10 Hz, 12dB/oct.
Semiconductor used Transistor : 32
Diode : 21
Pwer 100 VAC, 50Hz/60Hz
Power consumption 165W
External dimensions Width 450x Height 93x Depth 375 mm
Weight 11kg
Sold Separately Carrying Handle TO-1 (Left / Right 1 Set, ¥ 3,000)