Xref: utzoo sci.electronics:18242 comp.dsp:1347 Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!lll-winken!elroy.jpl.nasa.gov!swrinde!zaphod.mps.ohio-state.edu!unix.cis.pitt.edu!dsinc!netnews.upenn.edu!grad2.cis.upenn.edu!touch From: touch@grad2.cis.upenn.edu (Joseph D. Touch) Newsgroups: sci.electronics,comp.dsp Subject: Re: A question about the Nyquist theorm Message-ID: <38839@netnews.upenn.edu> Date: 6 Mar 91 16:47:51 GMT References: <625@ctycal.UUCP> <11515@pasteur.Berkeley.EDU> <3463@polari.UUCP> Sender: news@netnews.upenn.edu Reply-To: touch@grad1.cis.upenn.edu (Joseph D. Touch) Organization: University of Pennsylvania Lines: 34 In article <3463@polari.UUCP> mzenier@polari.UUCP (Mark Zenier) writes: >Some of the first ones used 1 D/A and sample and holds. The >BBC wanted to broadcast monophonic off of some CD's. With >the half sample time delay, it made the signal sound terrible. WHAT??? I saw the few posts about the time delay alledgedly IMPOSED by using a single D/A. A little thought reveals that using 4 sample and holds and 1 D/A removes the time delay completely, and S/H's are cheaper than D/A's. S/H1 locks the D/A output for the left channel as it comes off the CD, S/H2 does the same for the right channel. S/H's 3 and 4 grab the values of S/H 1 and 2 just before the next set of values gets locked in, resulting in an output completely in phase. Joe Touch PhD Candidate Dept of Computer and Information Science University of Pennsylvania Time 1 2 3 4 CD L1 R1 L2 R2 L3 R3 L4 R4 D/A L1 R1 L2 R2 L3 R3 L4 R4 S/H 1 L1------L2------L3------L4----- S/H 2 R1------R2------R3------R4------ S/H 3 L1------L2------L3------L4------ S/H 4 R1------R2------R3------R4------