From: shetline@bbn.com (Kerry Shetline)
Newsgroups: rec.audio,rec.video
Subject: Re: Selecting an LD Player
Followup-To: rec.audio,rec.video
Date: 4 Jan 1993 04:10:05 GMT
Organization: BBN
Distribution: world
NNTP-Posting-Host: bbn.com

Bill Alford writes:
>Hi Kerry,
>  I can get a lot more detailed on this, but my sonic observations point
>out that you've missed something vital. I have a new Rotel 955 CD
>player. Adding a Laser Illusions spatial filter (just a donut shaped
>device over the laser to better focus the laser) made a nice difference
>to the resulting sound. Further adding a Simply Physics Isodrive (a
>machined piece of plastic to completely clamp the CD) made a very
>noticeable improvement to the resulting sound. All of this was through
>the same rest of the system. From what I've read so far, your
>theoretical discussions don't account for this. I wonder why? 

I can think of two reasons for an actual change in the sound you
perceive, but I do consider them unlikely.

1) Apart from the electronic signal that gets to the speakers and then
to your ears, there are mechanical noises from the transport that more
directly enter the listening room. The devices you mentioned could
affect the mechanical sound of your CD player, thus changing the sound
that reaches your ear without actually affecting the electronic signal.
If this were the nature of the effect, it could be reduced (or nearly
eliminated) by using headphones, or by having the CD player in a
different room from your speakers. I doubt that this mechanical noise
argument is what the manufacturer's literature contends.

2) Your CD player, unaided, has such an inherently high error rate due
to optical and/or mechanical problems that it is constantly making
errors that are not catastrophic, but can be, and are, fixed by
interpolation. The devices mentioned could improve optical and
mechanical performance in such a way as to reduce this error rate. The
unaided error rate, however, would have to be unreasonably high,
probably at least an error or more per second, yet somehow not cause
severe errors that would result in skipping, popping, clicking, etc.
Even on cheap players, errors rates are usually so low that many discs
can be played before even one error requiring interpolation occurs.

What I do consider most likely is (and I hope that I can say this
without automatically triggering a defensive response) is that you
imagine the difference. If you've read what I've written previously
about our sense of hearing, you should know that this is not a
denunciation. The hearing process requires active use of expectation,
thus it is very susceptible to suggestion. This can be exemplified by
the common phemomenon of unintelligible song lyrics that, once
recognized, become intelligible *and actually sound different*. If you
can accept this premise, then a meaningful discussion can be had. If you
are utterly and entirely unwilling to consider the even the slightest
possiblity that the effects you hear are imagined, or if you simply
don't mind paying for placebos and prefer your (Laser) Illusions
unshattered, I will, of course, be unable to persuade you.

I certainly do not give any credence to the 'spatial filter' or the
'Isodrive' simply because they are marketed items -- that is, I
reject the arguement that "they couldn't sell them if they didn't
work." In fact, 'spatial filter' reeks of High Techo-Drivel.

It is not just my personal prejudice, but a simple matter of what it
means for something to be 'digital': Numbers are numbers. Bits are bits.
If the same sequence of bits, with the same timing, issues forth from
the digital output of a transport, then a particular DAC will respond in
the same way. If the tweeks you've mentioned don't ultimately effect
this bit stream, *they cannot effect the audio signal*. And there is
very little for these tweeks to do to the bit stream. Data errors are
rare, timing is well maintained, and nearly anything that over stresses
the tracking, timing, or data transfer from a CD will result in
catastrophic failure, not subtle sonic effects. (This either-everything-
is-fine-or-it-blows-up character is a common feature of digital systems.)

-Kerry
Newsgroups: rec.audio