I got a new 3 Leaf Proton the other day, and while it is generally a brilliant envelope filter, I thought the decay time was a little long. Anyway, I read about the limited edition Fromel models that had an internal switch to adjust the decay, so I thought I'd have a look inside mine. Lo and behold, my one has the switch, with the label "decay" below it! The up position seems to be a shorter decay. This isn't mentioned in the manual. Whatever - now my Proton can be everything I hoped for. Mine is model # 315 by the way.