Technical Description
distortion is unpleasant to hear, but the inaudible ultrasonic distortion is also undesirable, since it can damage valuable Loudspeaker System tweet-
ers. You will never experi- ence 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% (equivalent to 0.3% harmonic dis- tortion), the Power Guard activates the PG light and a dy- namic 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 pre- served. The MC205 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 MC205, there is a high current power supply for the five power amplifier channels. Refer to figure 18. The very large Power Transfomer, has toroidal windings on a toroidal core and can supply over 35 amps of continuous current. Refer to figure 19 (golf ball is for size comparsion). It is enclosed in the legendary McIn- tosh Potted
Enclosures and weighs over 12.06kg. The super size main filter capacitors can store over 310 Joules of energy for the five
amplifier channels, necessary for the wide dynamic range that “Digital Audio” demands. Refer to figure 23. 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 MC205 is equipped with a circuit that provides remote Power Control from a McIntosh A/V Con- trol Center. When the A/V Control Center is switched On, a (+5V) signal operates the power relay in the MC205. The MC205 also has a remote Power Control input for Zone B operation (two of the five channels).
Block Diagram
of the
Power Supply
Figure 18
17