Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site mordor.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxl!houxm!houxz!vax135!floyd!cmcl2!seismo!ut-sally!mordor!sjc From: sjc@mordor.UUCP Newsgroups: net.audio Subject: CDs: why no square waves? Message-ID: <3821@mordor.UUCP> Date: Tue, 12-Jun-84 04:34:34 EDT Article-I.D.: mordor.3821 Posted: Tue Jun 12 04:34:34 1984 Date-Received: Wed, 13-Jun-84 00:12:48 EDT Organization: S-1 Project, LLNL Lines: 37 >now, back to my favorite passtime of flaming CD's.... > >If they are sooooo good, them how come they naver can produce a >square square wave? >All of you out there who insist on seeing measurements and alike >before evaluating something never seem to notice that a CD has >never produced a (nearly) square wave. Either they cannot produce one >or the test disk was not properly written (and nobody is even trying >to make a proper one)[test disk that is]. >Whay you all seem to miss is that the CD square wave has a decaying >sine wave across the top and bottom of the square where it is supposed >to be flat. >Even the SHURE V15 type II can produce a more square wave. A square wave is equivalent to an infinite series of sinusoids. No matter how perfectly a CD reproduces the components below 22kHz, it cannot reproduce the components above 22kHz, so its square wave is doomed. The Shure V15 type II reproduces the components below 22kHz more poorly than does the CD, but since it reproduces some components above 22kHz (albeit even more poorly), its square wave looks "squarer". I suggest, Mr. Pearson, that you perform two experiments, using a high quality audio system. Find a signal generator which produces square waves and sine waves of the same RMS amplitude. First, record a 10kHz square wave at 0dB on a cassette and play it back, using a dual-trace scope to compare the original with the copy. Then connect the signal generator to the auxiliary input of your preamp, and alternately listen to a 10kHz square wave and a 10kHz sine wave. In the first case, I find the difference horrifying; in the second, it's almost imperceptible. Analog tape recorders have a rough time of it: not only do they have trouble reproducing high frequencies at full amplitude due to tape and head saturation, they have phase-shift problems considerably messier than those which have generated so much controversy with respect to CDs. --Steve Correll sjc@s1-c.ARPA, ...!decvax!decwrl!mordor!sjc, or ...!ucbvax!dual!mordor!sjc