Technical Description, con’t

tronic attenuator at the amplifier input reduces the input volume just enough to prevent any further increase in dis- tortion. The Power Guard circuit acts so fast that there are absolutely no audible side effects and the sonic purity of the music reproduction is perfectly preserved. The MC252 Power Amplifier with Power Guard is not limited to just the rated power output, but will actually produce distortion free output well above its rated power due to the McIntosh philosophy of conservative design.

Power Supply Circuits

To compliment the design of the MC252, there is a high voltage power supply for both channels. Refer to figure 20. The power amplifiers draw high current from the AC power line. Therefore, it is important that they plug directly into the wall outlet.

Also, most owners desire that there be one power switch for the whole audio system. The MC252 is equipped with a circuit that provides remote Power Control from

your McIntosh Preamplifier or Control Center. When you turn on your preamplifier a digital “1” (+5V) signal oper- ates the power relay in the MC252. The MC252 also has a remote Power Control Out Jack. The Power Control signal from this jack is delayed by a fraction of a second so that the turn on power surge of the next power amplifier occurs at a later time. This helps prevent power circuit overload that could trip circuit breakers or blow fuses, a very impor- tant feature in a high power Home Theater System employ- ing three MC252 Power Amplifiers.

The MC252 can provide greater than 50 amperes peak output current to drive uneven speaker loads. Some poor speaker designs have input impedance that dip to 1 or 2 ohms at various frequencies and the MC252 has the output current reserve to drive them. The MC252 has main filter capacitors that guarantee an excellent signal to noise ratio and the energy storage necessary for the wide dynamic range that “Digital Audio” demands.

Block Diagram

of the

Power Supply

Figure 20