Doepfer

Hi all,

This morning I was having a quick look through the new Analogue 
Systems group and noticed a comment that Bakis made about not being 
able to get Doepfer envelope generators to auto-repeat. So, thinking 
cap on and schematic of A-140 in hand I sat down, and after some 
while I came up with a simple way to do it. With an extra diode, 
resistor and op amp I have lashed it up on some breadboard and have 
been playing with it for the last hour or so, and it seems to do the 
job. All it does is sense when the envelope has got down to the 
sustain level, and then generates a pulse that is fed back into the A-
140 retrigger input, and hey-presto, auto-repeat!

A little more thought suggested that the op amp currently used for 
the inverted envelope output could be used to do this - thus with a 
few pins, cutting a track or two, add a couple more components, and 
this could be turned into a nice little mod to the module. The 
new 'sustain level reached' signal would be output at the old 
inverted output and fed back to the re-trigger input for auto-repeat -
 if this was taken through an A-150 switch one could also select its 
use via voltage control.

I haven't worked out the full details yet, but I expect it would be 
about the same complexity as what I suggested to fix the problem with 
the A-150 (anybody else actually had a go at doing that by the way?). 
I thought I'd run it by people first to see what the interest is, if 
any (what might seem simple to some may not be so for others...!). 
(On the other hand I might just buy another A-140 and do it anyway.)

As for the A-141, I note that there are currently two unused op amps 
already on the board, so it's conceivable that the same sort of trick 
might work with it too - I'll have a ponder on that too.

Cheers,
Tim