ark@rabbit.UUCP (12/01/83)
There is an obvious experiment to try. Several people, Sony among them, now make gadgets to turn a video recorder into a digital audio recorder. Take your favorite super-duper analog program source: LP12/Asak/Ittok, Studer half-track deck playing live master tape at 30 IPS, what have you. Copy from said program source onto digital tape. Now for the playback. Run the original source and the digital copy in parallel, making sure that the levels are matched to within 0.1 dB. Give the listener a pair of switches: one goes from one source to the other, the other does noting but interrupt the signal for a few milliseconds. The switch box should be wired so that not even the experimenter knows which switch is witch. A single listener should be left alone in a room through the entire running time of the program material. The listener's goal is to decide which switch is which. Repeat this experiment several times for each of several listeners, with several different program sources. The listeners should be people like the editor of the Absolute Sound. This is the simplest experiment I can think of which would be able to establish whether or not something is "wrong" with digital recording. In particular, the double-blind switching and the 0.1 dB level matching are ESSENTIAL. Has anyone done such an experiment? Care to point us at the results? Some of you may recall that I posted a note several months ago describing an experiment very similar to this one that demonstrated that listeners were unable to distinguish between the sound of different power amplifiers once the level and frequency response were accurately matched.
rfg@hound.UUCP (12/02/83)
Have you ever tried to match any two sources within 0.1 db? I know how to do it in principle and given the right equipment to work with. And there is an EQ on the market that supposedly incorporates a special circuit to do that. So practically no one has either of the forgoing. Let me ask you: suppose that you have matched them within 0.1 db as you specified, how do you demonstrate to me that you have done so? I hope we don't have to resort to such hairsplitting to squelch the monster-wire fringe. Can you find me two loudspeakers matched within 0.1 db? As a practical matter I doubt we can do much of anything within that tolerance over the band of concern. hound!rfg
crandell@ut-sally.UUCP (Jim Crandell) (12/05/83)
>There is an obvious experiment to try. > >Several people, Sony among them, now make gadgets to turn a video recorder >into a digital audio recorder. Take your favorite super-duper analog program This is an excellent idea, except for one minor flaw. When you're comparing two different signal sources in this manner, you have to synchronize them very accurately. From experiments with delay lines, I've learned that a person with a good sense of pitch can easily recognize the insertion or removal of a 200-microsecond delay in most program material if the transition can be accomplished quickly enough. I'd guess that you'd have to lengthen the dead time in the switches to a point at which the maximum possible sync error becomes inconsequential; .5 second, say. -- Jim ({ihnp4,kpno,ut-ngp}!ut-sally!crandell or crandell@ut-sally.UUCP)