smb@ulysses.UUCP (Steven Bellovin) (04/09/85)
Recently, five of us -- Steve Bellovin (ulysses!smb), Lynda Feng (hound!llfe), Jim Johnston (alice!jj), Andrew Koenig (research!ark, aka alice!ark), and Barbara Moo (attunix!bem) decided to A-B two CD players. Our primary interest was the effect of 4x oversampling with a 14-bit D/A converter versus a straight 16-bit DAC. We compared a Sony CDP-101 (a single 16 bit DAC multiplexed between both channels) with a Magnavox (Philips) SL2020. Other equipment used included a Heathkit AP-1800 preamp and AA-1800 250 watt/channel power amplifier/toaster oven, a pair of Bose 901 speakers, and a loudly purring cat for vibrato effects. (The ultra-thick cables were relegated to the trunks of our cars, for use in jump-starting.) The ouput levels of the two units playing a test disc was measured with a voltmeter; they matched to (well) within 1%. We compared several different pieces, including Neville Marriner's recording of the Brandenburg Concertos (Philips), Trevor Pinnock's rendition of the Chromatic Fantasy and Fugue, Tom Koopman's recording of the Toccata, Adagio, and Fugue in C (both Archiv), and the well-known Telarc recording of the Saint-Saens "Organ" Symphony. One of us (ark) has an extensive musical background. The test was informal: we hooked both CD players up to the preamp, put a copy of the same CD in each, synchronized them, and then listened to the music while switching back and forth. Note that this was not a blind test, although we closed our eyes at times. Anyway, the test took place in a house on a hillside surrounded by trees that therefore doesn't need blinds. The results: *no* difference at all was perceptible when the two players were properly synchronized. However, such synchronization was quite difficult to achieve, and mismatches often appeared to be sound reproduction differences. Specifically: on several occasions, we thought we heard a difference in sound quality between the two machines. In each case, we noticed that they were significantly out of sync. When we matched them more accurately (by blipping the fast-forward or reverse control on the Sony as appropriate), the apparent differences disappeared. In fact, it was often impossible for a listener with eyes closed to tell when the switch occurred. The importance of synchronization is worth bearing in mind when comparing a CD to an LP version of the same recording. We listened to several different types of music, including harpsichord and organ music (alice!jj indicated that such music would be more susceptible to the theoretical differences between the two approaches <at least given the material at hand, jj>). We listened to loud passages and to soft passages. We listened via speakers and via headphones. We listened to bass and treble. The results: *no* differences. A few other points worth mentioning: after a few hours of listening to these discs, listening to a solo piano on a disc from a ten-year-old analog master (Alfred Brendel's recording of Beethoven's "Appassionata" sonata (Philips)) made us think a snake was in the room -- the hissing had to come from somewhere, and the cat was still purring [Brendel's sensitive, articulate playing more than makes up for the amount of hiss on this recording --ark]. On the other hand, the digitally-mastered CD of Glenn Gould playing the Goldberg Variations showed some hiss as well, possibly from the mike preamps [solo piano is kind of a worst case for hiss --ark,jj]. Jumping up and down on the floor next to the Magnavox unit only (once) made it mistrack, but did tend to scare the cat. (Incidentally, we did not notice any distortion in the cat's purr noises from the presence of another cat in the same room.)
sambo@ukma.UUCP (Inventor of micro-S) (04/09/85)
Please forgive my ignorance, but what is the significance of the cat?
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Samuel A. Figueroa, Dept. of CS, Univ. of KY, Lexington, KY 40506-0027
ARPA: ukma!sambo<@ANL-MCS>, or sambo%ukma.uucp@anl-mcs.arpa,
or even anlams!ukma!sambo@ucbvax.arpa
UUCP: {ucbvax,unmvax,boulder,oddjob}!anlams!ukma!sambo,
or cbosgd!ukma!sambo
"Micro-S is great, if only people would start using it."ark@alice.UUCP (Andrew Koenig) (04/10/85)
> Please forgive my ignorance, but what is the significance of the cat? > ----------------------------------------- > Samuel A. Figueroa, Dept. of CS, Univ. of KY, Lexington, KY 40506-0027 42.
seifert@mako.UUCP (Snoopy) (04/11/85)
In article <1592@ukma.UUCP> sambo@ukma.UUCP (Inventor of micro-S) writes: > > Please forgive my ignorance, but what is the significance of the cat? The cat functions as a dynamic bad-sound absorber. He/she/it moves around from time to time so as to obtimize bad-sound absorbtion(sp). The optimum color for the cat is "LP vinyl black", as black absorbs better. The cat must be specially trained to not purr, meow, knock things over, or shed any hair, which might find it's way over to the turntable. The self-intelligent, self-portable bad-sound absorber is a must for the very highest levels of sound reproduction. However, these specialized cats are quite rare, and distribution is limited to certified golden-ears. (I don't have one myself, being only a silver-ear.) _____ |___| the Bavarian Beagle _|___|_ Snoopy \_____/ tektronix!mako!seifert \___/
crandell@ut-sally.UUCP (Jim Crandell) (04/12/85)
> > Please forgive my ignorance, but what is the significance of the cat? > > ----------------------------------------- > > Samuel A. Figueroa, Dept. of CS, Univ. of KY, Lexington, KY 40506-0027 > > 42. Really? Where did you find the rules to that version? -- Jim Crandell, C. S. Dept., The University of Texas at Austin {ihnp4,seismo,ctvax}!ut-sally!crandell