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MC402
Commentary

A stereo power amplifier with a double differential amplifier circuit.

Two out of four push-pull signal circuits are paired to form a balanced amplifier circuit, and a unique double-differential amplifier circuit that reintegrates the output with the output autoformer on the final stage. This realizes a perfectly symmetrical balanced transmission of the signal system from input to output, reducing all noise and distortion.
In addition, the output transistor elements are thoroughly selected to improve linearity.

Equipped with a Macintosh traditional output auto-former that can maintain constant operation regardless of the impedance of the speaker.
In addition, this auto-former absorbs back electromotive force from the speakers and prevents distortion from increasing.

Equipped with a power guard function, the input and output waveforms are always compared, and when the difference exceeds 0.3%, the gain is automatically reduced to suppress distortion.

Equipped with a sentry monitor, if the output current or voltage is likely to exceed the specified value due to output short-circuit or abnormally low load impedance, it automatically lowers to a safe level to prevent accidents.

With built-in thermal protection, when the sensor detects overheating, it shuts off the input and automatically recovers when the temperature drops.

It is equipped with in-rush protection that limits inrush current when power is turned on and reduces stress to the power supply circuit.

It is equipped with a turn-on delay that delays the start of the amplifier by approximately 2 seconds when the power is turned on and protects the speaker from transient noise.

With DC protection, if a DC component leaks into the output, the output auto-former protects the speakers by bypassing the ground.

The power meter on the MC402 is not a simple signal voltmeter ; it measures voltage and current and displays the actual power output to the speaker terminals.
In the WATTS position, the peak power display is provided with a slow recovery function. In the HOLD position, it returns slowly while holding the indicated value at the maximum peak level.
In addition, LIGHTS OFF is the position where the backlight turns off in WATTS display.

It adopts a 3-dimensional design of 12 mm thick glass and an illumination panel using LED / light diffusion fiber.

Stainless steel plates are used for the chassis, and a natural air-cooling system using a large heat sink is adopted.

Equipped with equipped with a remote power control which can turn the power on/off all at once from a control amplifier made by Macintosh.

Model Rating
Type Stereo power amplifier
Rated output Stereo : 400W + 400W (2 Ω, 4 Ω, 8 Ω)
Mono parallel : 800W (1 ohm, 2 ohm, 4 ohm)
Frequency characteristic 20 Hz ~ 20 kHz + 0 -0.25 dB
10 Hz ~ 100 kHz + 0 -3.0 dB
Total harmonic distortion factor Up to 0.005% (250 mW to rated output)
Cross modulation distortion factor 0.005% maximum (SMPTE at rated output)
Input Sensitivity / Impedance Unbalanced : 1.9V/10k Ω (with VR)
Balance : 3.8V/20k Ω (with VR)
Signal-to-noise ratio (A-base) Unbalanced : 85 dB
Balance : 115 dB
Damping factor 100 (8 Ω)
Power Guard Clipping prevention, total harmonic distortion <2% (overdrive <14 dB, 1 kHz)
Pwer 100 VAC, 50Hz/60Hz, 12A (UL/CSA Standard)
External dimensions Width 445x Height 226x Depth 445 mm
Weight 47.6kg