Re: Lionheart CD: The Distorion Chronicles

[dbk@tove.cs.umd.edu (Dan Kozak)]

In article <22084@hydra.gatech.EDU> gt4586c@prism.gatech.EDU (WILLETT,THOMAS CARTER) writes:
>In the early days of CD it was a very common error for the record companies
>to master the CD with an old master tape which was EQ'd for LP production.

This is true enough, tho' the EQing involved was of a more artistic nature than 
described below, more along the lines of "what would sound better on an LP?"
LPs (and CDs) can also be EQed (limited, etc.) at the actual mastering stage 
(i.e. during the transfer from the master tape to disc or whatever).  I've 
heard that the _Led_Zeppelin_II_ album had a fair amount of extra bass added
at the mastering stage (for the LP) but because the instructions for doing
so were on a bit of paper relating to LP mastering, the EQing wasn't done
to the first CD pressings, making them sound thin (this is 2nd hand info,
btw -- I don't have a CD player).

>Because of the physics of playing vinly, the LP master tape was EQ'd to have
>exaggerated high frequencies (so your needle could detect the wiggles) and
>de-emphasized low frequencies (so your needle wouldn't have to track too far
>side to side).  The phono input of your receiver has an equalization network
>to restore the proper equalization so your record sounds normal when you
>play it.  

On the other hand, this is (partly, and for the purposes of this discussion)
bunk.  Yes, there is an EQ curve (the RIAA curve) applied to the signal before
and after cutting a phongraph record, but it is not applied to the signal 
that is recorded on the master tape, it is applied to the signal just as it
goes to the cutting head of the lathe.  If you think about it, you'll see
why.

>However, if you master a CD with the LP master tape, you not only
>get a bad sound because there's no compensation in your CD input line, you
>can also get distortion due to the overloading of the digital channels.  

Digital doesn't distort, it glitches.  The difference is painfully 
obvious to anyone who has heard the difference.  A tape prepared for
LP cutting would be _less_ likely to distort, but I'll work that into
my theory of what's happened.  To wit:

If you hear distortion on peaks (i.e. the loudest points of the recording)
the problem is probably _not_ the CD, but some other component (best guess:
preamp) of your system.  The CD is producing (cleanly) a peak that causes
distortion in your system.  Why not on another CD?  Perhaps that CD _was_
mastered differently and had had extra limiting applied, (or was made from
a master tape that had been designed for LP and therefore had extra limiting
to cope with the smaller dynamic range of an LP).  Since the peaks had been
limited, your system didn't distort.  Obviously, I'm working with very little
data so there's no way I can be sure about this, but it makes more sense
than anything I've heard yet.

#dan

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