optocouplers (was:RE: Re[4] ...)

gstopp at fibermux.com gstopp at fibermux.com
Thu Oct 24 18:10:56 CEST 1996


     You are absolutely correct - the opto's provide constant current and 
     therefore linear charge/discharge curves. This at first did not really 
     concern me (because I was so happy to have found such a simple trick) 
     but now you are starting to make me worried!
     
     I initially thought that having linear slopes would not be that bad, 
     and actually that it would be different which is a good thing. But now 
     I'm thinking that I may not like the sound.... I must say that I don't 
     have enough linear envelopes around to make a good comparison. Even 
     though my 911's can be trimmed to truncate their attack and be 
     somewhat linear (for example a pitch rise using an AR shape will reach 
     its goal quickly and without slowing down), they are still really 
     exponential in their creation and the discharge slopes are distinctly 
     R/C in shape. Maybe I should play with my D-50 more often...
     
     I agree with Chris - the ability to select your slope would be the 
     most useful implementation. 
     
     Of course feedback is easy, but now this means that we need to add 
     voltage summers to each control input! Perhaps good for a new design 
     but like you say it does not bode well for ASM-1 applications. 
     Remember that any addition will need to be added to each ADSR in the 
     system independently. Perhaps, since the opto's control depends on 
     current into the internal LED, there is a simple way to add currents 
     without adding a voltage summer? Okay guys, think trickey!
     
     - Gene
     gstopp at fibermux.com


______________________________ Reply Separator _________________________________
Subject: optocouplers (was:RE: Re[4] ...)
Author:  Haible_Juergen#Tel2743 <HJ2743 at denbgm3xm.scnn1.msmgate.m30x.nbg.scn.de>
at ccrelayout
Date:    10/24/96 1:11 PM

But the Optocouplers ... wouldn't they be quite *linear* (i.e. nearly 
constant current charge/discharge) ?
     
I hope this will not ruin the whole thing ... If you have to add feedback 
as well, the major advantages would be gone (ease of use and 
potential-free action).
     
Please tell us when you have first results !
     
JH.




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