[sdiy] Simple AR tips

[Ian Fritz]

At 12:20 PM 9/18/2004, Peng wrote:
>I just finished one (of the many) AR envelopes, for the most part it's the 
>Charles Broduer schematic. Consists of 2 diodes, 2 pots, a 741, couple 
>resistors, and LED. I tended to avoid these designs but I'm expecting a 
>MIDI to trigger board from Mr. Maddox and needed envelopes that would 
>reflect the trigger velocities.
>  First problem was the envelope would slow up considerably when it gets 
> close to zero. Not good for percussion. I fixed that by using an offset 
> trim (striaght from TL071 data).

You didn't give us a link to the schematic, but it sounds like you are 
seeing a common symptom of simple EGs.  As the envelope decays towards 
zero, the resistance of the switching diode becomes large, increasing the 
RC time constant.  I also find those tails highly annoying.  There are 
simple circuits available for compensating for the diode drops.  I like 
these better than just truncating the response, which I believe is what you 
are describing.

   Ian




>   I've just started experimenting with the AR so if anyone has any 
> opinions or suggestions or tips, please let them flow. Such as capacitor 
> types ( found that polyester SEEMS quicker than the specified 
> electrolytic ). I would like to tweak the response curves but not sure 
> how to approach it.
>   Any techniques for employing velocity in patches would be very 
> interesting to hear about.
>
>Thanks,
>P.
>
>
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