McIntosh MR 77 Brochure
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Extracted text from McIntosh MR 77 Brochure (Ocr-read)
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Mclntosh research is a continuous program of exploration for new technology that permits performance improvement and greater value for you. This intensive research program developed the new technology necessary for the realization of these two new design concepts for the MR 77. 1 THE LINEAR PHASE IF FILTER Even since the beginning of FM, research engineers have realized that constant delay, or linear phase, IF filters were necessary for low distortion reception. Crude approximations to constant delay have always been used in FM tuners - with disappointing results. So-Called "Butterworth" or "Legandre" filters offer only a fair compromise with respect to delay error. Crystal and ceramic filters, usually based on the "Chebychev" model, work fairly well and give good selectivity, but none of these are constant delay (linear-phase) filters. Commercial tuners using these filters can show 5% stereo IM distortion at 100% modulation, and have delay errors up to 100%. In sharp contrast, the linear phase filter allows a tuner to show only .1% IM distortion at 100% modulation and has a delay error of only 1.2% in the useful bandpass. In its useful bandpass, it is a true mathematical approximation to linear-phase - the world's finest selective, linear-phase, minimum-phase shift filter. A FORTRAN computer program using an algorithm that took six years to develop was used in its design. The mathematical complexity of the filter design procedure is almost beyond belief. Using a process called "numerical integration in the complex S-plane," a high speed IBM 1130 computer spent eighteen minutes on the design of the MR 77 IF filter. A human engineer, working twenty-four hours a day and seven days a week, would have taken 300 years to finish this work . . . assuming he made no mistakesl 2 LINEAR PHASE BRIDGE DISCRIMINATOR The linear phase filter would be useless if it had to work into an ordinary FM detector. Thus a new detector with suitably low distortion had to be developed. A search of the available literature revealed a little-known bridge circuit with a theoretical distortion of zero! However, designing a practical working circuit for a commercially feasible stereo tuner took some doing. A U. S. patent is pending on this circuit. Distortion performance of the bridge detector is close to the theoretical zero. In addition to its excellent distortion performance, the bridge detector also exhibits capture ratio close to 0 dB. The linear-phase bridge discriminator uses a balanced transmission line bridge in conjunction with a differential voltage-doubling rectifier to achieve 99.9% accuracy demodulation of FM signals. The only adjustments in the MR 77 detector are two simple variable resistors. These resistors center the tuning meter and set the transistor bias. Complex tuning for minimum distortion is not needed. YOU ARE PROTECTED WHEN YOU BUY MCINTOSH Every Mclntosh instrument - every one - is tested to be equal to or better than the performance limits advertised. When a performance limit of 0.2% harmonic distortion is established for an instrument, Mclntosh means that every, each, all of the instruments manufactured must be capable of performance to that limit - or better - or your full purchase price is refunded. One of the reasons Mclntosh can make this promise is that we 100% test each of the instruments for maximum performance. We are not content knowing that 10% of our instruments are tested and meet the performance requirements established by our engineering group. We must know that all of the instruments meet the requirements. This vigorous pursuit of excellence takes time. At Mclntosh more time means more care, more protection for you. There's no production rush at Mclntosh. "What does this mean to investment in research, an continuous testing; throug urement can we promise life, performance, highest Mclntosh offers you a F TRACT. During the first dime for service. Mclntosh guarantees labor. It costs of a Mclntosh, the conserv ticated appearance make greater value when you a to Mclntosh now.
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$699.00 Walnut Veneer Cabinet. $29.00 me?" you ask. Only through an impressive d professional test instruments, through product analysis; and endless meas- and deliver to you reliability, long value, and freedom from service. REE THREE YEAR SERVICE ON- hree years you can't spend one guarantees parts and Mclntosh you nothing. The extended life ative ratings and the sophis- a Mclntosh instrument a e ready to trade. Step up