gt4586c@prism.gatech.EDU (WILLETT,THOMAS CARTER) (02/15/91)
Recently I had posted that my copy of the Lionheart CD contained alot of distortion which appeared to be due to improperly EQ'd master tapes being used. A few comments were made about the quality of exported master tapes and the generally poor quality of american CD production. i am now happy to report that i have found a clean copy of the lionheart CD after three tries at two different record stores. as it turns out, my original copy was pressed in West Germany way back in the days before all albums were defiled by the UPC label. The two bad copies I got from one record store were US pressings from EMI-Capitol USA. The finally good copy is an EMI-Manhattan pressing. 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. 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. 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. It appears that the early releases of Lionheart suffered this fate but that it has been corrected. Of course the record companies don't offer to replace your garbage CD with a good one nor do they even generally admit they screwed up - they just quietly slip the new version into circulation with no change in catalogue number to let you distinguish between the versions. I guess the moral of the story is to be wary buying used CDs of older albums. Or if you are a rabid LP fan, the moral is to stay away from CDs generally. -- thomas willett Georgia Institute of Technology, Atlanta gt4586c@prism.gatech.edu "Violence is the last refuge of the incompetent." - Salvor Hardin (Foundation)
dbk@TOVE.CS.UMD.EDU (Dan Kozak) (02/18/91)
In article <22190@hydra.gatech.EDU> gt4586c@prism.gatech.EDU (WILLETT,THOMAS CARTER) writes: >In the interest of trying to guess the source of the nastiness on my copy >of the Lionheart CD, i'll make a few comments as to why my system is >blameless. First of all, when i use my cd player i set my PS Audio 4.5 >preamp on STRAIGHTWIRE, so there is essentially a direct connection between >the amp and the CD player, and therefore I cannot be overloading my preamp. Ok, quick test: set everything up as you have described and then turn off power to the preamp. Do you still get sound? If so, then your preamp's STRAIGHTWIRE setting _is_ a passive connection and your conclusion is valid . . . if turning the preamp off causes sound to cease, then their is some active component in between (buffer amp or whatever) that could potentially be distorting. Next check, hook the CD to the amp directly (ain't component systems grand? :-) >Second, my amp is not causing the distortion because 1) my Adcom GFA-555 has >distortion lights which go blinky-blink when the amp starts to clip, and >these lights never came on, and I can't make any definitive comments on this other than to wonder what these lights are supposed to show, i.e. output stage distortion, input stage distortion, driver stage, or what? I know that Adcom makes high quality gear, so I'm sure that these indicators indicate something important, the question is what. (see next item) >2) the distortion can be heard at all volume >levels, from very quiet to loud. Important info. Where is the volume control in this circuit? On the power amp, or on the preamp? What is being indicated here is that the distortion has occured/is occuring before the volume control. Depending on the placement of the volume control, this could include the input stage of the power amp, the input stage of the preamp, the buffer stages of the CD player itself, or of course, the source material. >That leaves the only possible system >culprit as the CD player, and I think we both agree that it is >impossible to overload a properly designed CD player. Mmmmm . . . depends on how you define "properly" :-). Since there do seem to be audible differences between CD players, I have to assume that there is room for variation between them -- headroom in the filtering and buffer amp stages may be one variable parameter. When I said that digital doesn't distort, I was referring to record, not playback (see next item) and in any case the buffering and (possibly) filtering stages of a CD player are analog. >I think, therefore, that the distortion was recorded onto the CD. The next >question is where in the recording chain did it appear. If the RIAA >equalization is applied to the cutting lathe after the master tape, then I >guess that somebody got really lazy with the track level settings when >mastering the master CD and let them overload. But that would produce glitching, not distortion. A digital audio signal models an analog waveform as a series of numbers that represent the amplitude (level) of the waveform at discrete intervals. The highest amplitude signal would be represented by a binary number where all bits are 1. As I understand it, when a signal louder than this comes along, the sampling circuitry gets confused and produces a binary number that is, for the purposes of this discussion, random (it's not actually, but in audio terms, it might as well be). So overmodulating a digital sampling stage produces "glitching" which sounds something like dropping in very short samples of Einsteuzende Neubatten or a metal foundry or a full tilt aerial assault over top of everything. It _does_not_ sound like the analog distortion (or tape saturation, or whatever) that we all know and hate. Of course it's completely possible (tho' unlikely, mastering engineers are well paid for a reason) that the distortion occured in some analog stage on the path between the master tape and the first digital stage. It's not likely that the master tape itself is the culprit, since I've never heard that _Lionheart_ was remixed for CD, so the master tape is presumably the same one used for LP and the other CD, etc. If your really interested in this, you could try A/Bing a few components to see if a different CD player makes a difference, etc. (you could also try the CD on other complete systems) I do know of at least one recording (_What's_New_ by Linda Ronstadt) where the mastering (in this case LP) was so hot that the peaks would distort almost any phono preamp out there. I know this because my father uses it to show off _his_ design (which it doesn't distort), but I wonder about everyone else out there . . . On the other hand, I don't remember _Lionheart_ being very peaky, rather the opposite. As Alice once said, curiouser and curiouser . . . #dan Clever: dbk@cs.umd.edu | "Softly her tower crumbled in the Not-so-clever: uunet!mimsy!dbk | sweet silent sun." - Nabokov
lazlo@TRITON.UNM.EDU (Lazlo Nibble) (02/18/91)
Look, this is really a simple thing to figure out. My Lionheart
pressing is:
CD: 198? UK (EMI CDP 7 46065 2: matrix CDP 746 065-2 2895 256 01.)
It's clean, no distortion anywhere that I can tell. Look at your
Lionheart disc, post the catalog and matrix number (the matrix number
is on the inner hub of the CD) and where you've noticed problems, and
then the rest of us can check our discs, look to see if they're the
same pressing as yours (same matrix number == same pressing) and check
our discs where yours has problems. If someone has the same pressing
as yours but can't find any distortion, it's your system. If they
find distortion too, it's the CD.
Lazlo (lazlo@triton.cirt.unm.edu)
-------------------------------------------------------------------------------
FLASH! Intelligence of human race decreasing. Details at...uh,
when the little hand is on the....