18Technical DescriptionMcIntosh Laboratory, the company who introduced theworld's first amplifier that could be called "High Fidelity",has done it again. The McIntosh engineering staff has cre-ated a power amplifier without compromise, using the mostadvanced McIntosh circuit design concepts.A continuous average power output rating of 200 wattsand with an output current of greater than 50 amperes perchannel, making this the most advanced Integrated Ampli-fier McIntosh has ever manufactured. The distortion limitsfor the MA6900 are no more than 0.005% at rated poweroutput for all frequencies from 20Hz to 20,000Hz. Typicalperformance at mid frequencies is less than 0.002%. Thetrue distortion readings on the MA6900 are so low, it takesspecial measuring techniques to make accurate readings.The MA6900 can deliver the best possible performancefrom any type of high quality loudspeaker system.Creating an amplifier with this level of performance didnot come easily. Many months of design, testing and mea-suring were required. Extensive controlled listening tests,the ultimate form of measuring, were made before the finaldesign was accepted.Preamplifier Design PhilosophyAll signal switching in the MA6900 is done by Electro-Magnetic devices. Electro-Magnetic Switching is a proventechnology that uses the latest in materials and manufactur-ing methods. Each switch consists of a glass tube that isfilled with an inert oxygen-free atmosphere and sealedwith tiny leads protrudingfrom either end. These leadsextend into the tube andoverlap one another with aseparation of a few thou-sandths of an inch. The leadsare made from a ferrous ma-terial that is influenced by amagnetic field. They are firstplated with gold as a basematerial, then with rhodiumand finally ruthenium. Ru-thenium is the best contactmaterial known.The glass assembly isthen placed in the center of amultilayer coil of copperwire. The entire assembly ismolded together in a toughshock absorbing material.Bottom Inside View of the MA6900The switch and coil connectors extend from the bottom inthe form of printed circuit board terminals. When a DCvoltage is applied to the coil, current flows and creates aEqualizer Control Adjustment RangeHz (Hertz)dB(Decibel)Figure 10
