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MC252
Commentary

A stereo power amplifier equipped with two technologies representing the Macintosh, a balanced circuit and an output autoformer.

It can be used as a high-power monaural amplifier as well as a stereo power amplifier.

It uses a unique Macintosh balanced circuit for all stages and a round configuration with a total of 16 power transistors in four parallel, reducing distortion and noise in all bands to unmeasurable levels.

A constant output is obtained regardless of the load impedance by the traditional Macintosh output auto-former.
The auto-former also plays an important role in maintaining the normal operation of the amplifier by letting the back electromotive force, which is inevitably generated by the movement of the vibration system of the speaker, escape to the ground.

The power supply section is equipped with a large toroidal transformer.

It employs a large heat sink with a heat radiation area of over 1000 square inches (6,452 square centimeters) and a unique variable tracking bias system. This realizes low-temperature operation even though it is a naturally air-cooled structure without using a fan, thereby extending the life of the amplifier.

A highly reliable multiple protection system is installed as a protection circuit.
The Power Guard constantly monitors the input and output waveforms and automatically reduces the gain to reduce distortion when the difference exceeds 0.3%. The Sentry Monitor automatically reduces the output current or voltage to a safe level when the output current or voltage is likely to exceed the specified value due to an output short or abnormally low load impedance to prevent accidents.
Temperature protection detects overheating, shuts off the input, and automatically returns when the temperature drops. Rush protection limits the inrush current when the power is turned on to reduce stress in the power supply circuit. Turn-on delay protects the speakers from transient noise by delaying the start-up by approximately two seconds when the power is turned on.
It is also equipped with DC protection, and the auto-former protects the speaker by bypassing the DC component leaked in the output.

Low distortion and high output have been achieved by adopting a balanced circuit in which both the left and right channels supply power to each circuit independently.

Equipped with Blue Eyes Power Meter.
This meter is designed to respond almost ten times faster than VU meters used in commercial equipment and to indicate a 2 kHz single-cycle tone burst signal level with 95% accuracy.
In the WATTS position, the pointer reaches its peak point and remains stationary for a period of time visible to the human eye before returning to its original position. In the HOLD position, hold position, the pointer remains at the maximum level as long as there is no further input, and returns at a slow speed of 6 dB / min.
In the OFF position, the backlight is off, but the meter continues to operate in the WATTS display.

It is equipped with a remote power control function that can turn the power on / off all at once from the control amplifier of the Macintosh, and series control of multiple units is possible.

Equipped with two types of input terminals : balanced and unbalanced.

A mirror-finished stainless steel chassis is used.

Model Rating
Type Stereo power amplifier
Rated output Stereo : 250W + 250W (2 Ω, 4 Ω, 8 Ω)
Mono bridge : 500W (4 Ω, 8 Ω, 16 Ω)
Mono Parallel : 500W (1 Ω, 2 Ω, 4 Ω)
Frequency characteristic 20 Hz ~ 20 kHz + 0 -0.25 dB
10 Hz ~ 100 kHz + 0 -3.0 dB
Total harmonic distortion factor 0.005% or Less (250 mW ~ Rated Output)
Cross modulation distortion factor 0.005% or Less (SMPTE at Rated Output)
Input Sensitivity / Impedance Balance : 3.2V/20k Ω
Unbalanced : 1.6V/10k Ω
Signal-to-noise ratio (A-criterion) 85 dB (unbalanced)
112 dB (balanced)
Damping factor 40
Speaker output 1 System x3 (for 2 Ω, for 4 Ω, for 8 Ω)
Input terminal RCA : 1 system
XLR : 1 system
Power Guard Clipping prevention
Total harmonic distortion factor <2 per cent
(Overdrive <14 dB, 1 kHz)
Pwer 100 V, 50Hz/60Hz
Power consumption 8A (UL/CSA Standard)
Maximum external dimensions Width 445x Height 240x Depth 376 mm
Weight 42.9kg