[sdiy] That 2180 with modular cv??

Julien Delgoulet jdelgoulet at free.fr
Tue Jun 28 08:46:31 CEST 2011


You can have a look at Alain Coupel web site : http://www.acxsynth.com/VCA/vcafr.htm
This is a single 2180/2181 based VCA. Easy to build (require just two opamps and a few resistor). And work prefectly.

Jules

Le 28 juin 2011 à 03:22, dan snazelle a écrit :

> yes as i said , i was using a summing amp with a negative gain as per the demo circuit datasheet (a different sheet than the basic datasheet)
> 
> sorry if that wasnt clear
> 
> 
> however it still thumped quite a bit
> 
> however I just found a circuit that might help !
> 
> check it out
> 
> (2150 is untrimmed version of 2180)
> 
> 
> http://m.bareille.free.fr/modular1/vca_dbx/mb_dbxvca.htm
> 
> 
> 
> I am pretty sure someone out there is using the 2180's for vcas
> 
> i think there might even be a eurorack module that uses them
> 
> 
> 
> On Jun 27, 2011, at 8:54 PM, David G Dixon wrote:
> 
>> ... or, of course, you could use just the one summing amp at a max gain of
>> 0.2, and use the other pin.
>> 
>>> The datasheet says that the control pins are to be limited to 
>>> +/-1V.  If you feed an undivided gate or envelope signal to 
>>> the control pin, the VCA will clip hard.  I would sum a CV 
>>> attenuator pot and a CV bias pot (the latter injecting 
>>> voltages from 0 to 5V into the summing node) pots to convert 
>>> any control signal (e.g., 0/+5V, 0/+10V, or -5/+5V) to 0/-5V, 
>>> and then invert the result at a gain factor of 0.2 to 0/1V 
>>> and use the circuit in Figure 2.
>>> I'm not sure whether you'd want to use the Ec+ pin or the Ec- 
>>> pin (I haven't looked at it that closely -- in either case, 
>>> the unused one is grounded), but the main point is that the 
>>> THAT 2180 is about 5 or 6 times more sensitive to control 
>>> voltage than the SSM2164.
>> 
>> 
> 
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