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Sound On Sound Q. Just what is sound on sound? I have a tape deck with this function. I've heard that you can keep adding different sound tracks on one channel, yet with my deck you can have only two tracks recorded on each other, unless you go through a confusing process and record the two tracks over to the other channel and add another sound track (making three) via speaker and a microphone. I use the tape monitor switch on my receiver for this purpose. Would buying a microphone mixer solve my problem? In buying a mixer, I notice that a mixer usually ranges from either $5 to $20 or $80 to $250. What is the difference? -Alexander Stewart, Tallapososa, Ga. A. A tape recorder which truly incorporates a sound-on-sound provision does the following. Record Signal 1 on Track 1. Play Signal 1 and record this simultaneously with Signal 2 on Track 3 (no speaker is involved in this step or any of the following steps). Play Track 3 (containing Signals 1 and 2) and record this simultaneously with Signal 3 on Track 1. Play Track 1 (Signals 1, 2, and 3) and record this simultaneously with Signal 4 on Track 3, etc. All this, of course, is on a mono basis. If you want stereo sound-on sound, you will need 4-track heads and suitable mixing and switching facilities; alternatively, you will need an extra 2-track playback head mounted before the erase head, plus the necessary mixing and switching facilities. The more expensive mixers provide better quality and more flexibility, and usually provide gain. The cheaper mixers may be passive devices without gain. Square Wave Reproduction Q. In "Equipment Profiles" one sees from time to time reproductions of square waves used as a criteria of the quality of a given piece of equipment. Yet over many years of reading Audio, I have never seen a reproduction of the playback of a square wave recorded on a tape recorder. Why? I tried it on my unit and got back something that barely resembles a square wave. When making a bias adjustment, would adjusting to reproduce and record the best square wave be a useful way of making such an adjustment? -Charles L. Thomas, Tempe, Arizona. A. A square wave, as can be shown mathematically or with electronic apparatus, consists of a fundamental frequency and an infinite number of odd harmonics. For example, a 1,000 Hz square wave would consist of a 1,000 Hz sine wave plus sine waves of 3,000 Hz, 5,000 Hz, etc. As a practical matter, a good square wave can be reproduced by a piece of electronic equipment if it is capable of handling the first ten odd harmonics. Because a tape recorder has limited high frequency response, it cannot adequately reproduce a square wave for the higher frequencies; it can only do so for the middle and lower ones-say from about 1,000 Hz down. To illustrate, reproduction of a 1,000 Hz square wave requires that the tape recorder have virtually flat response to about 21,000 Hz. This can be done by the better machines today, but not all that easily. By comparison, a good audio preamp or power amp can get out to 100,000 Hz, making it possible to reproduce square waves to about 10,000 Hz. I don't see any basis for adjusting bias by using a square wave. (Source: Audio magazine, Feb. 1975; Herman Burstein) = = = = |
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