The ADSR circuit

ldavid at lae.lad.gmeds.com ldavid at lae.lad.gmeds.com
Tue Feb 6 19:50:06 CET 1996


> 
> Ric Miller had problems with this circuit, so it may not be
> drawn correctly.  I had it going originally on a breadboard
> (16 years ago!) so between that and the final text something
> might have gotten screwed up. Open to any helpful suggestions
> that would save me from building it up again and checking it
> out!
> 
> Barry
> klein_b at a1.wdc.com

Isn't this great?  I ask a question about a book and the author 
answers!  The following will probably only make sense if you have 
Electronic Music Ckts and can refer to it while reading this; but I 
know many (most?) of you do...  (If you don't, buy it! :)

I actually do have a suggestion.  I haven't been able to breadboard 
the ckt, but from looking at it I think there's one small problem.  
Without the trigger I think it would work fine, but I don't think 
the retrigger will work as shown.  The description says; 
"Retriggering the envelope is made possible by allowing a pulse from 
comparator A4 to reset the flip-flop, causing the output of NOR gate 
No. 1 to be a logic 1."  As far as I can tell, a trigger will reset 
the ff, but it will also cause the output of NOR gate 1 to be a 
logic 0.  (A low Q is logic 0 at the right input, but the 
trigger is a logic 1 at the left input of the NOR.)  Basically a 
retrigger would act like the gate signal going back down, i.e. it 
would start the release section of the EG.  

My suggestion is to put a blocking diode between the comparator A3 
output and the flip-flop reset (with cathode to the reset).  This 
should not affect the gate signal resetting the ff (just another 
0.7V drop), but it will block the trigger from getting to the 
left-hand input of NOR gate 1 and acting as a logic 1.

Let me try a crude asciimatic:

Comparator A3                NOR Gate 1
  |\                            |   |
  |  \--->|----x----------------x   Q of flip flop
  |  /         |
  |/           V  <---this is suppposed to be a diode symbol!
              ---
               |
               x----R of flip flop
               |
               |
               |
  trig pulse --x


I hope this makes sense; and I humbly submit to correction by those 
more experienced than myself.  ;)  What do you all think?

ld
--
----------------------------------~~~~~~~*--------------~~~~~~~*    
Larry David                    "I no longer live, 
ldavid at lae.lad.gmeds.com        but Christ lives in me." 



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