Doepfer

Hi Ethan/Paul,
My 140 is marked 'v1 1995' and was bought in 2001 - my guess is that 
it is thus very unikely that there are 2 versions out there (either 
one of you may be able to correct me though!).

As for the round/flat LEDs, I would guess that when Doepfer do their 
designs they would try and stick to parts from a 'preferred parts 
list', which would contain component types that are available from at 
least one manufacturer (I think this is called 'second sourcing'). 
This minimises the danger of not being able to get components of a 
certain type should one manufacturer decide to stop making them (i.e. 
to avoid the situation that exists with certain of the CEM chips!). 
Thus whether LEDs are flat or round probably depends on which type 
they managed to get the best deal on last time they bought some in.

That leaves the question of what might be the cause of any perceived 
difference between units. The circuit is relatively straightforward, 
and with my limited knowledge my guess as to what it might be would 
fall on the capacitors which charge/discharge to give the envelope. 
All three, one for each of the 3 ranges, are 'electrolytic' types, 
which are notorious for having poor tolerances, even within one 
particular brand and nominal value. How much any differences might 
contribute to the shape of the envelope to the extent that they could 
be audibly perceived to be different, I do not know - hooking them 
both up to a 'scope would be the easiest way to _see_ the difference!
(The LED is quite isolated from the envelope generating part of the 
circuit, and so a different LED in itself will not affect the  
envelope!)

Tim


--- In Doepfer_a100@y..., Paul Schulz <dasfonk@w...> wrote:
> When I ordered two A-140 ADSRs and two A-145 LFOs  in September 
´98, one 
> half of the modules were delivered with flat-top and the other half 
with 
> round LEDs. But they have the same version-number, so I don´t know 
whats 
> up with that. Perhaps only a matter of design.
> You are right, the response of the flat-tops is much better and 
they 
> look more professional to me. My A-129 vocoder with flat-top LEDs 
looks 
> so clean...
> 
> Paul
> 
> 
> ethanzer0 wrote:
> 
> > Hello,
> >
> > I just picked up 3 used A-140s. 
> > They seem to be a little older
> > than the others I have and they
> > have flat-top LEDs versus the
> > rounded LEDs in my other A-140s.
> >
> > Did the A-140 go through a design
> > revision somewhere along the line?
> > I ask because I like the response
> > of the flat-top LED modules better
> > than my others.
> >
> > Thanks in advance,
> >
> > Ethan