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MC502
Commentary

This compact stereo power amplifier is based on the same design concept as the C504.

The Normal (green) and Limit (red) lamps on the front panel are operated by an originally designed circuit called a waveform comparison circuit.
In this circuit, the Limit lamp lights up and the Normal lamp goes out when the difference between the output waveform and the input waveform is 0.5%. When the difference reaches 1%, the power guard circuit operates to prevent clipping of the amplifier, to prevent distortion from being reproduced from the speaker, and to protect the speaker safely. In this case, the amplifier is still at its rated maximum output. The Limit lamp lights up when the amplifier is overloaded, and is lit for a visible period even when the overload condition is very short.
The input and output waveforms are compared by an IC operation amplifier, and the waveform difference due to distortion of the output waveform is converted into a voltage, which is amplified approximately 100 times and supplied to a Schmidt trigger circuit through a full-wave rectifier circuit.

Model Rating
Type Stereo power amplifier
Output
Stereo : 72W + 72W, Rated Output (2.7 Ω ~ 4 Ω)
50W + 50W, Rated Output (8 Ω)
Mono : 150W, Rated Output (8 Ω)
Rated output band 20 Hz to 20 kHz
Harmonic distortion factor 0.02% or less (both stereo and monaural, 20 Hz to 20000 Hz)
Frequency characteristic 20 Hz to 20 kHz, + 0 -0.25 dB
10 Hz to 10 kHz, + 0 -3.0 dB
Signal-to-noise ratio 95 dB or more (at rated output)
Output voltage 25V
Damping factor 50 or more
Input Sensitivity / Impedance 0.75 V, 2.5V/75k Ω
(Switched by level control)
Pwer 100 VAC, 50Hz/60Hz
Power consumption 20W ~ 400W
External dimensions Front Panel : 406 mm wide x 92 mm high
Body : Width 375x Height 60x Depth 368 mm
Weight 12.2kg