Doepfer

ok, now you got me thinking...if you take the inverted out of an envelope, run it thru a linear mixer, and add a voltage bias from the S&H as i describe, would it achieve the "zero crossing" Stu describes? can't test atm...


----- Original Message ----
From: Stu Grimshaw <grimshaw@stugrimshaw.com>
To: Doepfer_a100@yahoogroups.com
Sent: Tuesday, June 19, 2007 5:15:15 PM
Subject: [Doepfer_a100] Re: adding cv offset

> > 2. envelopes and lfo's can be swept into and out of negative voltages - so
> i don't need to
> > pull out a lead and plug it into a voltage inverter while i'm playing.
> 
> That's not the offset function but a polarizer ! You probably mix up
> positive/negative offset and positive/negative amplification. 

the voltage inverter, combined with the inverse output of an adsr, was only a next-best 
way of geting an envelope into negative voltages. what it doesn't do, however, is enable 
the adsr curve to cross the zero line - the whole time you're in either the negative or the 
positive. since an amplifier only multiplies and therefore cannot enable this zero crossing 
(or am i being dense here?) it's the offset that i'm interested in.

>Both is
> possible e.g. with the A-138c. So you probably ask for something like the
> two upper sections of the A-138c as a single module.

if the 138c polarizing mixer can produce a negative offset voltage, which seems to be the 
case, then that is exactly what i was suggesting :) at the time i posted the original 
suggestion, i was unaware that the 138c could do this. i am assuming that the gain of the 
second channel receiving the envelope cv is unity when fully clockwise. this would be 
important for a spontaneous patch addition on stage, since i don't have an opportunity to 
retune the vco after plugging the offset-able adsr into it.

florian's advice was also to use a mixer like everybody else, and i suppose i'll follow that 
advice. but since all i'm doing is adding a -ve offset to an envelope, it's just a pity that a 
mixer will be permanently wired immediately behind an adsr, with no use for half of the 
hardware on it, including the rack space :-)

cheers,

stu




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