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From: tldavis@athena.mit.edu (Timothy L. Davis)
Newsgroups: rec.audio.high-end
Subject: Re: Chesky Jazz Sampler & Audiophile Test CD
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Date: 12 Jun 91 12:47:58 GMT
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jvb7u@fermi.clas.Virginia.EDU (Jon Brinkmann) writes:
>I've been intrigued by advertisements for the _Chesky Jazz Sampler and
>Audiophile Test CD_.  >
>	After nine Jazz selections, each a showcase for the company's
>	proprietary 128-times oversampling technology, the _Chesky Jazz
>	Sampler Volume I_ offers conclusive tests to show the existence
>	of such disputed characteristics as (1) image height, (2) stage
>	width beyond the speaker's edges, (3) stage depth and (4) absolute
>	polarity.  These illustrations are so vivid that they can be
>	used to silence those who argue that such sonic properties are
>	'imaginary'.  This disk settles it, once and for all.

I have the CD.  

The musical selections sound excellent.  They are all soft jazz, each from a 
different recording, with a "liveness" and stage presence equal to the best 
small ensemble recordings I have heard.  Unfortunately the selections are
a bit more mellow than my tastes.  I might label them as "department store 
music," one step removed from elevator music. (Performers: the Pizzarellis,
Clark Terry, Phil Woods, Paquito D'Rivera etc.)

The "technical tests" part of the CD is a bit more annoying.  As for the
stage depth, height, etc., I am unconvinced that audio cues alone are
sufficient to judge whether the sound is coming from above or below the
speakers.  In fact, I can make a strong argument for a 2-way up/down ambiguity 
present in the signal unless the acoustics of floor and ceiling are 
completely different. But that's beside the point.  The CD TELLS YOU what
to expect as you are listening, so there is no way to form an independent
opinion.  After being told, its easy to say, "Oh yes, the speaker DOES sound
closer now". 

The worst technical test on the CD, however, is one which should be quite
useful except for its flaw.  There is a string of "bong" sounds, which are
near-perfect sinusoids which start at a high amplitude and decay.
Unfortunately, the 128x-oversampled (Chesky-style) bongs are clipped by
the high end of their A/D system.  It's a rather startlingly clean clip on
the oscilloscope.  The filtered-style bongs (conventionally sampled for
comparison) aren't clipped, but must have some (inaudible) distortion from the
antialiasing filters which are necessary.  They made a passing reference
in their newsletter to the "golden-eared" who had noticed this error, but
to me it was quite obvious both to my ears and to my oscilloscope that the
first three bongs were clipped.  I was frantic at first, thinking my CD
player output or amplifier was maladjusted, but it was that way ON the
TEST CD.  Big oops.  I guess Chesky won't be joining Hewlett-Packard in
the ranks of test signal producers.

The most useful test, to me, is also the most dangerous:  full-volume
(0 dB) square waves.  Running a square wave through your system is a decent
way to evaluate amplifiers, tape decks, etc. to assure that you have linear
phase and a flat frequency response, and boy let me tell you,
my Harman-Kardon TD392 "ultrawideband linear phase" cassette deck does bad 
things to the square wave, no matter what the dolby encoding or bias setting.
It is dangerous because, even at a low volume setting, a full-force square
wave generates high energy high frequency harmonics which could easily
melt your tweeters.  Wouldn't you hate to leave your house with soft jazz
playing, and return to find your audiophile speakers damaged?
In my opinion it was not a good idea to put both of these on the same CD.

My overall opinion:  the jazz sampler section is as good as any other sampler
CD, and the audiophile test section could have been improved.  I'd like to
see different tests, such as sinusoids of varying frequency, sawtooth waves,
etc. as a poor-man's function generator, and less emphasis on their 
"wonderful" 128x oversampling technology.  There are many ways to do
digital sampling well, and this incredible oversampling is not necessarily
the best way.  But Chesky would have you believe in their electronics and
nobody else's.  If there is a better test CD, I would buy it instead, and
get my jazz on a real jazz album.  (My current favorite: Michael Brecker,
Now you See it, Now you Don't)

Tim Davis (tldavis@athena.mit.edu)
Part-time sax player
Full-time PhD student
Zero-time MD student