Newsgroups: alt.folklore.urban
Subject: Re: CD Pens was:Re: I Have a FAQing Headache
From: dogbowl@dogbox.acme.gen.nz (dogbowl)
Date: Wed, 29 Jul 92 05:45:16 NZT
Organization: The Dawghaus BBS

roy@harlqn.co.uk (Roy Badami) writes:

> >>>>> In article <TeosNB5w164w@dogbox.acme.gen.nz>, dogbowl@dogbox.acme.gen.n
> 
>   dogbowl> There was a scheme a while back when most machines had a
>   dogbowl> single DAC to time correct the difference in time caused by
>   dogbowl> processing first one channel then the other.  From memory
>   dogbowl> the left channel was delayed 20 or 30 nanoseconds.  This
>   dogbowl> sold quite well until manufacturers started using dual DACs
>   dogbowl> in the machines.  What several electronics magazines
>   dogbowl> pointed out was that the same effect was obtained by moving
>   dogbowl> the left speaker *3millimetres* closer the the listener.
>   dogbowl> There was a tongue-in-cheek referencr to putting a 3mm pad
>   dogbowl> in the right earpiece for headphone usage. :-)
> 
> Ah, but it could be important if you want to derive a mono signal from
> the player.  Even if the disc is in mono (ie old recording), the phase
> shift will lose you a little high frequency response.  (Admitedly, in
> the case of a mono recording you could avoid this by just using one
> channel of the output.)  I doubt it would be significant in practice,
> though.
> 
> It _is_ still true that the early single DAC players didn't sound as
> good as the dual DAC ones, however, but _not_ because they only had
> one DAC.  These were generally based on the first generation Sony
> chipset, and generally weren't oversampled, whilst the competing
> designs were Philips-based machines with 2 14-bit converters running
> with x4 oversampling.  Also, I believe the early Philips DACS had
> better linearity then the early Sony ones....
> --

The Philips chipsets did sound a lot better than the Sony set, mainly 
because without the oversampling the Sony devices had to have brick-wall 
audio filtering, with attendant massive phase distortion.

Funny thing is, my Philips CD-350 player (bought in 1985) will still play 
scratched/damaged discs that a lot of players won't even look at. 
When I tried it out, it sounded better than just about every other player 
available ( even ones costing 4 times as much ), and played one scratched 
disc that I've never seen ANY other player play ( It was a defective CD 
of the sort that you used to find glued to displays. We ripped it off, 
and threw it in to see what would happen. )

That player still stands up pretty well sound wise against the latest 
players, though the absolute best player I've ever heard was a Denon CD 
cart player used for broadcasting use. It sounds better than Denon's 
domestic players which cost 4 times as much.

I found the article that I referred to in my earlier post, and to all 
people who emailed me saying that the pens reduce the servomotor 
loadings, the test also looked at the analogue output of the photodiodes, 
and found absolutely no difference with or without the pens.

For anyone who is interested in obtaining a copy of the article on CD 
pens, write to :


Silicon Chip Magazine
P.O.Box 139
Collaroy Beach 2097
NSW 
Australia.

The article was published in their December 1990 issue.
As they have full copyright, I can't repost it to the net without their 
express permission.

I don't know whether they can supply articles from back issues, they 
don't mention it in their reader services section.

They do have copies of that issue available however, at Aus$5 + $1 p&p 
for orders outside Australia.
If anyone wants to phone them, try +61 2 979 5644 ( They take credit 
cards )


dogbowl at The Dawghaus BBS  ( +64 6 357-9245 )


Newsgroups: alt.folklore.urban