Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site allegra.UUCP Path: utzoo!watmath!clyde!burl!ulysses!gamma!exodus!mhtsa!mh3bs!eagle!allegra!karn From: karn@allegra.UUCP Newsgroups: net.audio,net.flame Subject: Re: jj's Re: Thoughts on subjectivity and specifications Message-ID: <2248@allegra.UUCP> Date: Wed, 1-Feb-84 16:14:00 EST Article-I.D.: allegra.2248 Posted: Wed Feb 1 16:14:00 1984 Date-Received: Tue, 7-Feb-84 14:01:26 EST References: many, <779@drufl.UUCP>, <2387@rabbit.UUCP>, <782@drufl.UUCP> <2458@rabbit.UUCP> Organization: AT&T Bell Laboratories, Murray Hill Lines: 29 Regarding the "phase shift" complaint in CDs....again... THIS IS AN UTTER RED HERRING!!!!! The only people who complain about the "inherent CD player phase shift problem" are those who a) haven't looked at many CD player lab tests b) don't know the first thing about signal theory, and c) can't find any other term to latch onto to give their vague complaints some pseudo-scientific credibility. Take a look at the square wave and impulse response tests of the various CD players. For example, the Marantz player reviewed in the current issue of Audio. Notice the ripples on each side of the impulse or square wave edge. See how they're nice and symmetrical? This, BY DEFINITION, indicates linear phase, and many of the CD scope photos I've seen are practically textbook examples! The existence of the ripples in the first place is an inescapable result of the sharp (i.e., nearly ideal) AMPLITUDE response cutoff. Only if these ripples were asymmetrical would they indicate phase nonlinearity, in which different signal frequencies encounter differing delays in arriving at the output terminals. Now it is true that SOME CD player manufacturers have elected to simplify the design by using filters that do not provide linear phase. It is still doubtful that ANYONE can hear the difference at the high frequencies involved, but even if some could it is totally wrong to claim that "phase shift" is an inherent and unacceptable problem with ALL CD players. The fact that people are fighting major wars over such insignificant squabbles indicates just how close to perfection CD players really are. Phil Karn