17
Figure 21
of the two amplifier circuits, allowing each ampli- fier cir- cuit to be optimized using its own power supply. Refer to figure 20. High power
amplifiers draw high current from the AC power line. The very large Power Transfomer, has toroidal windings on a toroidal core and can supply over 35 amps of continuous current. Refer to figure 21 (golf ball is for size compar- sion). It is enclosed in the legendary McIntosh Potted Enclosures and weighs over 12.06kg. The super size main filter capacitors can store over 600 Joules of energy for the five amplifier channels, necessary for the wide dynamic range that “Digital Audio” demands. The power amplifier draws high current from the AC power line. Therefore, it is important that they plug directly into the wall outlet. Also, most owners desire one power switch for the whole audio system. The MC1.2KW is equipped with a circuit that provides remote Power Control from a McIntosh A/V Control Center. When the A/V Control Center is switched On, a (+5V) signal operates the power relay in the MC1.2KW. The MC1.2KW 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 important feature in a high power Home Theater System employing three or more MC1.2KW Power Amplifiers.
Figure 18 With Power Guard
Figure 19
Without Power Guard
Technical Description, con’t
audible and inaudible distor- tion levels exceeding 40%. The audible distortion is unpleasant to hear, but the inaudible ultrasonic distortion is also undesirable, since it can damage valuable loudspeaker system tweeters. You will never experience the harsh and damaging distortion due to clipping.
The Power Guard circuit is a waveform comparator, moni- toring both the input and out- put waveforms. Under normal operating conditions, there are no differences between the shape of these waveforms. If an amplifier channel is overdriven, there will be a difference between the two signal waveforms. When the difference exceeds 0.3%,
the Power Guard activates the PG light and a dynamic electronic attenuator at the amplifier input reduces the
input volume just enough to prevent any further increase in distortion. 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 MC1.2KW 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 fully balanced design of the MC1.2KW there are two high voltage power supplies; one for each
CIRCUIT
BREAKER
Block Diagram
of the
Power Supply
Figure 20
