![]() ![]() had become the format for single records, and 33 1/3 r.p.m. While changing sides no more than once, if at all. The big appeal, of course, is that listeners could hear entire symphonies or Broadway selections on 33 1/3 The jukebox industry gave a big boost to the 45, but classical music and Broadway cast albums, from such shows as ''South Pacific,'' made 33 1/3 the format of choice. (The development of multi-speed turntables made this a bit easier.) For a brief time, many recordings were available in 78, 45 and 33 1/3 formats, but as far as sales were concerned, plummeting figures suggest that many consumers headed to the sidelines and waited out the fight. ![]() record the following year, and the struggle that followed is referred to as ''the battle of the speeds,'' and it went on for years. RCA Victor responded with the seven-inch, 45 r.p.m. RCA was less thanĮnthusiastic, so CBS went at it alone, offering the new discs, as well as inexpensive players, in 1948. 1 competitor, RCA Victor (they of the earlier, disastrous flirtation with 33 1/3), to facilitate the mass conversion to 33 1/3 format. The CBS folks were so convinced they had the record of the future in their hands that they offered their new technology to their No. (Goldmark`s Microgroove could last up to 23 minutes per side). Heimers says that the 33 1/3 figure was essentially an arbitrary number, or more precisely a final compromise between sound quality and length of play The record, dubbed the Columbia Microgroove LP, was designed to rumble along at 33 1/3 r.p.m. Peter Goldmark devised a record that held between 224 to 300 grooves per inch (up until then, 85 grooves per inch was the norm) and delivered high fidelity, according to Gelatt`s book. In 1944, CBS commissioned more research into the long-playing record, and in 1947, achieved success. But getting more music out of the same size disc proved to be a perplexing technical problem the slower the record spun, the worse the sound quality became, and moving the grooves closer together was unworkable for several reasons. And if anybody is prepared to make a recording of a tone it would be interesting to add.But the notion of a slower playing speed persisted, the obvious attraction being that more music would fit on a record that didn`t spin so fast. Which rather gratifyingly meets the expectations. For 45rpm this has to rise to 337.5rpm/5.625Hz.Īfter making recordings in the two 45rpm states, processing the data and plotting the results produced, With the standard 50Hz drive the motor turns at 250rpm/4.17Hz. It occurred that I have two ways of making it got at 45rpm, either with the Lingo driving the motor proportionally faster or using the original big pulley adaptor and having the motor go around at the standard rpm. For 33rpm this is 0.56Hz and multiples, for 45rpm 0.75Hz and multiples.Īt present I only have an LP12/Lingo. Given that numbers are coming out how does one know they are sensible? I generated an FM modulated test signal that appeared to demodulate plausibly and then moved on to making some recordings of a test record.Īs no record is completely concentric, nor completely flat, we would expect modulation at the rotation rate and at some multiples. One applies FM demodulation to a mono wav file, the other applies quite large FFTs to the result and writes a text file suitable for plotting. It turned out that this book contained everything one needed to know to implement digital FM demodulation.Ī few evenings later I had a couple of crude programs. If the tone is demodulated then what comes out is a moment by moment measurement of the instantaneous rotational speed of the platter. In essence if a turntable plays a recording of a pure tone then any variations from a constant speed will manifest as a change in the frequency of the tone. A couple of weeks ago I came across this blog post and my interest was piqued.
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