[sdiy] Re: Moog ADSR

[Gene Stopp]

It's really a quite pronounced effect on my Mini, with the controls set
properly I can probably get over two octaves of VCF "opening". Perhaps it
has something to do with the fact that my machine is a really really old
model D. I forget the serial number but I've looked it up before. There's
not a single IC in the whole thing, all transistors. I've noticed that these
old ones have slightly different panel markings than the later ones - for
example, on the VCO fine tune knobs for oscillators 2 and 3, all of the
numbers are there (-5, -4, -3, -2, -1, 0, 1, 2, etc.) instead of every other
one, and around the attack and decay knobs on the EG's all of the
millisecond markings are there instead of just some of them. Anyone else
ever notice this?

If I were you Juergen, I'd add a switch!! I've actually patched an ARP 2600
to do the same thing - I used the sample and hold gated by the keyboard gate
to sample the tail end of the decay from the ADSR and add it to the filter
Fc. Worked great!

Best Regards,

- Gene


-----Original Message-----
From: jhaible at t-online.de [mailto:jhaible at t-online.de]
Sent: Tuesday, September 25, 2001 4:41 AM
To: synth-diy at dropmix.xs4all.nl
Cc: gene at ixiacom.com; dfevans at bbcr.uwaterloo.ca
Subject: [sdiy] Re: Moog ADSR


>   On my Mini I don't remember the effect being anywhere near this
> string.  It was noticable and useful as a performance feature but it
> wasn't really drastic.
>
> --
> David Evans   

> Minimoogs do have a "climbing" attack peak when Attack = 0 and 
Sustain <> 
> max. It's easy to hear on recordings, actually, try some old Rick 
Wakeman 
> with Yes or how about side 1 of the album "You" by Gong.
[...]
> - Gene

Thanks for your replies. So it was the Mini, not the Modular that shows
such an effect. I checked the schemos last night, and both EGs are
quite different, so I definitely made the wrong conclusion here.
I checked my circuit again, and I found the problem: my -6V regulation
was not strong enough. The integration cap on the Modular EG is 
connected 
to -6V (not to GND), so fast Attack times draw a lot of peak current
from the -6V supply. 
This will easily be cured with a LM337 instead of the simple opamp
I used. (I have local +12V / -6V regulation. The main supply is
a MOTM compatible +/-15V.)
But it was a nice effect. Maybe I should add a switch ...

JH.