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CX List Expanded In "High Fidelity News" Duly! at least one manufacturer of CX decoders-Audionics was not mentioned, although the company announced in January that it would be manufacturing decoders under license from CBS. We (Sound Concepts) and at least two other manufacturers also signed agreements with CBS before the Summer Consumer Electronics Show in June. To our knowledge. CBS announced all of these manufacturers at its press conference in early May. John J. Bubbers Vice President, Marketing Sound Concepts. Inc. Brookline, Mass. Our CX item was written some weeks before CBS's press conference, and rushed into print before we learned the names of the first CX licensees. The roster of companies offering CX decoders as of the June show comprises Audionics of Oregon, Sound Concepts, MXR. Phase Linear, and CM Labs, and the number is certain to grow.-Ed. AM Stereo Static The statement in "A Renaissance for AM Radio" [May] that AM stereo could possibly have a frequency response of 50 Hz to 8 kHz is very strange. In 1929 a leading custom installer of high fidelity equipment in New York City asked the company I worked for to build them an AM receiver with response from 50 Hz to 7.5 kHz. We said: "You can't use it, but if you insist, we'll build it." We built it. They were humiliated: The interchannel interference made the set worthless. We rebuilt it for response to only 4 kHz, and this time the set worked. The reason is simple: AM stations are as signed 10-kHz channel spacing. Because side-bands extend equally on both sides of the carrier, the maximum useful sideband is theoretically 5 kHz. Practically, though, space must exist between the sidebands of adjacent stations to avoid interference. Hence, AM receivers are usually limited to 3.5 to 4 kHz response. Occasionally. there is no interfering station on the next higher or lower channel, but atmospheric conditions may unexpectedly bring in distant stations. Perhaps we can have stereo AM, but not high fidelity AM. It couldn't be done in 1929, and it can't be done today. Many people are interested in AM stereo. Why not publish a comparison and evaluation of the various methods under consideration? Alfred Barber; Flushing, N.Y. The author was specifically asked not to include system comparisons because of the expected FCC selection of a single design. making all others moot. With reference to frequency response, a bandwidth of 8 kHz is possible under good conditions. using switchable IF. However, Mr. Barber is correct that with average or marginal AM reception. an effective bandwidth of 3 to 4 kHz would he more typical. -Ed. A Call for Balance I was alarmed to read (in the New York Times. June 18th) that the number of classical record reviews in your magazine is steadily decreasing I hadn't kept count. It would he unfortunate for classical music-or any other type of music, for that matter-to fall victim to your video section. Don't ignore video completely: just devote less space to it. Mark Judman; Freehold, N.J. In earlier days, HIGH FIDELITY was devoted primarily to quality coverage of audio equipment and classical recordings. More recently, the space devoted to classical music has been reduced while that for pop music, and now video, has been increased. What keeps me reading the magazine is the presence on your staff of such reviewers as David Hamilton, Harris Goldsmith. Andrew Porter, and Paul Henry Lang. so I am further disturbed to learn that consideration is being given to eliminating the thorough, lengthy critical discussion that has long distinguished HIGH FIDELITY'S reviews. Daniel Morrison; New York, N.Y. First we assure you that HIGH FIDELITY will continue its tradition of critical reviews, though the number may be less now than in the past. And, effective with this issue, our video coverage has been integrated into our new design, with the result that it takes less space. -Ed. Darrell Anniversary Congratulations on the recent twenty-fifth anniversary of the valuable feature, "The Tape Deck." Sincere thanks to R. D. Darrell for his interesting and helpful reviews of music avail able in the reel-to-reel and cassette formats. The heading on the second portion of his May column, "The Old Reliables," could be modified slightly by dropping the s and applied to Darrell himself. By fortunate coincidence. my musical tastes are close to his. Over the years. upon the arrival of my issue of HIGH FIDELITY, I have opened it first to "The Tape Deck." Nelson B. Dodge Sun City, Calif. Letters should he addressed to The Editor. High Fidelity, 825 7th Are.. N.Y.. N.Y. 10019. All letters are subject to editing for brevity and clarity. --------------------- Also see: ACOUSTIC RESEARCH (AR) speakers [ad]
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