Mon Jan 10 17:57:34 EST 2011

Evelopes again

1. Decay needs to be exponential

2. Attack, well...  The low-pass exponential is a hack anyway as there
   is no real physical relation.  Attack is either instantaneous, or
   it is "blown" or "bowed", i.e. a consequence of human actuation.

So what about sticking to the exponential converter anyway, design for
accurate large range decay time, and find a hack to make attack longer
than instantaneous. 

Maybe here switched resistors could work.