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by Herman Burstein Prerecorded Tape Noise Q. I have a question with regard to a peculiar noise problem in prerecorded tapes. In some instances I have noted suddenly that a previously satisfactory tape gives very loud clicking noises. There is no periodicity, but the points at which noise occurs are constant. The volume of the noise at its worst is far more than the loudest recorded level on the tape. The noise does not appear to be erasable. Otherwise, the sound quality is not impaired. -D. A. Berlincourt, Chagrin Falls, Ohio A. I suspect that the clicking sounds you describe were put on the tape as the result of a static discharge. Perhaps this happened during rapid wind or rewind. It may be best for you to consult on this problem with the manufacturer of your tape machine. Twisted Tapes Q. Some of my tapes tend to become somewhat twisted or distorted so that they do not go smoothly over the playback head. This happens even when the tapes are handled very carefully, and involves only a small percentage of the tapes. -D. A. Berlincourt, Chagrin Falls, Ohio A. Plastic substances often have memory, and this might account for the physical twist developed by some of your tapes. The twist might develop during storage as the result of a portion of the tape being under high stress, particularly if it was rapidly wound or rewound just prior to storage. Tapes tend to keep best if they are stored after being run at normal operating speed. If a tape has long been in storage, stress can perhaps be relieved by winding and rewinding the tape before using it again. Plastic Cap for Heads Q. It occurs to me that people with three or more heads on their machines might benefit by some type of plastic cap that would fit over the heads that are not in use. Sometimes I use my recorder in the playback mode for 50 to 100 hours without recording. I'm getting just as much wear on the record and erase heads as if I were using them. Wouldn't one benefit from some kind of plastic shield to slip over the heads? -L. N. Norman, Winthrop, Iowa A. Your thought about a plastic cap is an interesting one. I'm wondering if one could achieve about the same effect with a thin piece of celluloid (or similar material) attached with tape to the heads in question. I am not sure whether this would or would not significantly disturb the tape path. Where tape tension rather than pressure pads is used to maintain tape to head contact, the use of a plastic cap or device such as I have suggested might interfere with good contact between the tape and the desired head. Dolby System Function Q. A friend of mine has told me that the Dolby system will not reduce the hiss on tapes that have been previously recorded. Rather, he says, the Dolby will prevent any new amounts of hiss from being added to a tape when it is being recorded. This, it seems to me, runs counter to what I have read about the performance of the Dolby. Thus one report stated that "a played-back signal ... is identical with the original in frequency response, but with a reduction of tape hiss of the order of 10 db." To me this means that if I re-record one of my own tapes through the Dolby, the hiss level in playback will be reduced 10 db. Am I correct? -David J. Churchill, APO San Francisco. A. Your friend is correct. The Dolby will not reduce noise of already recorded materials-unless you are willing to accept a drop in treble response along with a drop in noise. If flat response is to be maintained, the Dolby keeps noise to a minimum only in making a new recording, whether off the air, live, or of a disc or another tape. Chromium Dioxide Tape Q. If chromium dioxide tape is so good for cassettes, why has it taken so long to appear in open reel tapes? -Charles Novitski, Pasadena, California A. As with any new product, a new tape formulation has its problems in terms of compatibility with already existing equipment. These problems include amount of bias, amount of audio drive current, and record equalization. Thus, existing tape machines would have to be adjusted or modified, in all probability, in order to work satisfactorily with the new formulation. However, a new cassette machine can be designed from the start to work properly with a new tape formulation. (Audio magazine, May 1973; Herman Burstein) = = = = |
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