Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!lakesys!mikes
From: mikes@lakesys.lakesys.com (Mike Shawaluk)
Newsgroups: comp.dsp
Subject: Re: More digital mixer stuff
Message-ID: <1160@lakesys.lakesys.com>
Date: 29 Sep 89 15:45:46 GMT
References: <9238@pyr.gatech.EDU> <1989Sep29.102204.8798@ivucsb.sba.ca.us>
Reply-To: mikes@lakesys.UUCP (Mike Shawaluk)
Organization: Lake Systems - Milwaukee, Wisconsin
Lines: 33

In article <1989Sep29.102204.8798@ivucsb.sba.ca.us> todd@ivucsb.sba.ca.us (Todd Day) writes:
>byron@pyr.gatech.EDU (Byron A Jeff) writes:
>~>Remember that since you are using an analog MUX, the samples can't all
>~>be done at EXACTLY the same time, so there will be a slight delay between
>~>all of the channels.
>~I'm brand new in this domain. I have no clue what the effect of the
>~delay between channels will be. Can you give me an idea?
>
>Ch 1 - delay - Ch 2 - delay - Ch 3 - delay - Ch 4
>
>The delay will be the length of time it takes to switch from one
>channel to the next via the MUX and then sample with the sample/hold.
>Probably not very signifigant, but those who spend $1000 on interconnects
>for their stereo systems would probably complain.  Of course, they wouldn't
>be listening to digital, anyway, would they? :-)

Well, the delays would be eliminated if you used 4 sample & holds, up before
the analog demux, no?  Simply "hold" all 4 signals at the same time, and then
demux them after they are frozen, then unhold & repeat the sequence.  Of
course, the other solution would be to have separate A/D's for each channel,
as has been suggested in an alternate thread of this same subject.

BTW, isn't this "delay" the same "problem" that's been mentioned with certain
CD players, which use only one D/A converter for both channels, but mux the
stereo outputs?  One person (in a review I read) gave the analogy of standing
1 cm closer to one of the stereo speakers in the room while listening to a
CD, as being the effect of this phase shift (i.e., the speed of sound vs. the
delay).

-- 
   - Mike Shawaluk 
       (mikes@lakesys.lakesys.com  OR  ...!uunet!marque!lakesys!mikes)
   "If spirit == essense, then spiritual == essential!"  - me