wjm@whuxk.UUCP (08/02/83)
Tis true ... we don't really know (yet) what quantifiable parameters that can
be objectively and reproducibly measured on a lab bench affect CD sound.
Is 1kHz square wave response significant ? Is the cut off (due to a 44.1 kHz
digital sampling rate) at about 22 kHz (and the effects introduced by the
player's low pass filters in the D/A converter significant? At present, we
don't know but I think one of the key points is that we'd better find out.
Last night, I received in the mail a blurb from Linn Products (who are not
exactly unbiased, given that they make high-end analog record playing equipment)
presenting some British hi-fi magazine A/B tests between a Linn Sondek TT with
Linn Ittok arm and Linn cartridge (with a Linn head amp) feeding the same
preamp, power amp, and speakers as the Sony CDP-101 CD player. They then A/B'd
CD and LP versions of the same works (both classical and popular) mostly EMI
European releases. The panel preferred the Linn setup to the CD's.
I am not against CD's (far from it, I'm looking forward to a virtually scratch-
proof, warp-proof medium that is also free of surface noise (CBS take note))
but I want something that compares favorably to the best analog recordings
(some of which are digitally mastered, and almost all are cut at half-speed)
like Telarc, Nautilus, Mobile Fidelity, and Sheffield, when played on a high
end system costing the same price ($1K - 1.5K) as today's CD players (like
the Linn, or a Sota with a good arm, or a Mission 775/774). The thing is
now to find the characteristics that define superior performance in a CD player
and to present those in a test report.
Bill Mitchell (whuxk!wjm)
Disclaimer: the opinions expressed here are my personal ones, and not necessarily
those of my employer, Bell Laboratories..kimr@tektronix.UUCP (Kim Rochat) (08/05/83)
The latest Absolute sound elaborated on the Linn material mentioned by Bill
Mitchell. - For the Sony CD player, the rise time was 60 micro-seconds
(compare with 16us for a Shure V15-V).
More obvious was the observation that above 7.4 Khz, square waves turned to
sine waves! (If you think about it, the first odd harmonic of 7.4 Khz is
~22Khz). Now we can all put on our favorite headphones and tune our signal
generators to 7.4 Khz and switch the function between sine and square waves
to see if the difference is audible or not.
Kim Rochat
tektronix!kimrnewman@utcsrgv.UUCP (Ken Newman) (08/05/83)
It is true that listening to a signal generator at 7.4 kHz and switching between sine and square waves would reveal no audible difference, but this proves absolutely nothing! The speaker/headphone cannot reproduce the 7.4 kHz square wave accurately anyway, so you would NOT be comparing sine with square, but sine with sort-of-square-sine-almost. Transducers are not as nice as electronics. Square waves are nasty test signals.