McIntosh MC 2205 Brochure
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Page 1
Higher power demands on amplifiers have presented music listeners with a form of unplesantness in listening, amplifier overload (hard clipping) that looks and acts like square waves. Clipping is caused when the amplifier is asked to produce more power output with low distortion than it can deliver. Clipping of a complex wave form is largely composed of odd order harmonics and intermodulation products. High order odd harmonics and intermodulation products are dissonant and are not musically related to the signal being amplified. They are heard as great RATIO OF PEAK TO AVERAGE TOTAL PRESSURE IN dB DISTANCE 2.0 PIANO 10 FT. 30 0 -30 20 100 1K 10K FREQUENCY IN HERTZ DISTANCE 2.1 PIPE ORGAN 12 FT. 30 0 -30 20 100 1K 10K FREQUENCY IN HERTZ 4.1 BASS SAXOPHONE 30 0 -30 20 100 1K 10K FREQUENCY IN HERTZ DISTANCE 3.5 FT. . Oscillogram of output waveform with and without Power Guard. Input overdriven for each trace 20 dB. Amplifiers when driven to clipping are capable of delivering up to twice the heat load to the loudspeaker. In addition, they can have more than 40% harmonic distortion. The extra heat energy content of the clipped signal will damage most speak- ers. Mclntosh leadership in engineering has developed a new circuit that ... (1) dynamically prevents power amplifiers from being overdriven into hard clipping ... (2) which reduces the heat developed in the loudspeakers ... (3) assures that the amplifier will produce its maximum output without increased distortion. That new circuit we call "POWER GUARD." HOW POWER GUARD WORKS In Power Guard, a waveform comparison circuit detects minute amounts of waveform difference between the output signal and the input signal. A sampling of the program material at the output of the amplifier is constantly compared with the program material at the amplifier input. You are alerted, by a front panel indicator, to waveform differences of 0.5%. Should the differences reach 1%, Power Guard goes to work. Power Guard dynamically reduces input level to prevent amplifier overload yet permits the amplifier to deliver its absolute maxi- mum power output without extra distortion. In addition, the output of the "waveform comparator" activates the front panel NORMAL and LIMIT indicators. Any time that the input circuit is fed excessive amounts of signal causing a waveform difference of 0.5% in the output the indi- cators change from green NORMAL to red LIMIT automatically and instantaneously. You are always assured that the power of your amplifier is as clean and distortion free as it can be. and disappointing discordance and distortion. In the past years Mclntosh has substantially improved the ability of amplifiers to deliver lower distortion within their rated power. The improvement has removed the masking of the unpleasant, harshly distorted sounds of clipping. Music demands high peak power reproduction ability without clipping. Although we may listen to surprisingly low average power output, the peak power requirements can be very high. Consider these graphs of the power demanded of an amplifier reproducing the pipe organ, the piano, and the bass saxophone. The charts show that the peak power demands is almost 30 dB or 1000 times the average power demand. Since it is necessary that these short interval power spikes be reproduced with low distortion, it means the average power output of the power amplifier must be limited to l/1000th of its capability or the listener must accept the discordant distortion of clipping.
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mizes heating. Additionally, when there is no signal output no output transistor is conducting." When there is no signal no output device is conducting. Conservative Mclntosh engi- neering keeps operating temperatures low assuring long life. -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 Output volts Load and limiting characteristics at 8 ohm output of MC 2205 The interleaved multifiler wound Mclntosh designed auto- transformer transfers all the power you paid for to all im- pedance taps. You are not power penalized for operating at an output impedance of less than 8 ohms. The Mclntosh auto- transformer does its outstanding job without adding phase shift, (common in other designs) limiting frequency response or power output. In short, the Mclntosh autotransformer is the ideal answer to a difficult problem. Heat sinks must be large and they must have adequate ventilation for proper cooling. The MC 2205 has 1100 square inches (7.64 square feet) of radiating surface. In addition, the chassis has been designed to permit the maximum amount of air to flow over the heat sinks to conduct away the life limiting heat. Mclntosh developed output monitoring meters add to your operating ability. The meters are unusually flexible in that they read directly in watts, can be made to hold the highest reading and continuously update on higher power or can be switched to be peak reading - peak locking decibel meters. When used as a watt meter all the information is direct reading, without conversions or complicated mathematics. In addition, as direct reading watt meters they are calibrated in average watts for a sine wave signal but respond to signal peaks. Ordinary meters are incapable of indicating the short in- terval information in a sound wave. The mass of the meter movement is too great to respond to the nearly instantaneous changes in music program material. That short interval infor- mation can have a duration as short as one-half of one thou- sandth of a second. Should the meter be capable of the high velocity movement the human eye could not perceive the information. Mclntosh engineering pursued both problems electrically. By developing new electronic circuits the meters are made to respond to short intervals with an accuracy of 98%! To permit the eye to see such high speed motion the electronic circuits that drive the meter pointer are time stretched so the meter pointer position can register in the persistence of vision characteristics of the human eye. To achieve long trouble free life in an amplifier it is essen- tial to have cool operation. Cool operation is the result of careful design of the output circuit. Correct matching of the output circuit to the loudspeakers with an autotransformer and a mechanical layout that uses generous sized, adequately ventilated heat sinks complete the design for cool operation. The use of bipolar expitaxial output transistors in the Mc- lntosh output circuit allows the amplifier to operate as cool as possible. The predriver, driver, and output stages are fully complementary and have high circuit efficiency which mini- 12 10 8 6 4 2 0 -2 -4 -6 -8 -10 -12 Output current in amps With the Mclntosh MC 2205 power amplifier you are Mclntosh protected in five ways must be capable of meeting its published performance limits or you get your money back. No other manufacturer offers you this money back guarantee of performance. 5. The famous Mclntosh 3 Year Service Contract protects you from any cost of repair for three full years because Mclntosh will provide all parts, materials and labor needed to return the measured performance to the original performance limits free of any charge. The SERVICE CONTRACT does not cover any shipping costs to and from the authorized service agency or the factory. rise above normal through restricted ventilation or other causes, the AC is disconnected from the amplifier by an automatic heat sensing relay. The AC will be restored when the temperature returns to normal. 3. Any DC component in the output circuit from whatever cause is shunted to ground through the Mclntosh autotransformer. You and your speakers are protected completely from this kind of amplifier failure. 4. Mclntosh gives you a money back guarantee of performance. Your Mclntosh instrument 1. The patented Mclntosh Sentry Monitoring circuit constantly monitors the output signal. At signal levels up to rated output this circuit has high impedance and has no effect upon the output. If the power output exceeds design maximum, the Sentry Monitoring circuit operates to limit the signal to the output transistors. In the event of a short circuit across the amplifier output or severe impedance mismatch the Sentry Monitoring circuit wilt protect the output transistors from failure. Both positive and negative halves of the output signal are monitored independently. 2. Should the temperature of the heat sinks