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ADSR Integration
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ADSR Integration

by CDX on Wed May 28, 2014 4:24 pm

Hi there, this is my first post here in this forum and I need a hand to put me in the right direction. Any help would be appreciated. Thanks in advance.

So I have a full adsr and want it to shape the vca of my xoxbox. My question is which point(s) should I connect it to? Or where is the input point for the original env. to modulate the vca? I've searched this forum for some time but had no luck.

Would anyone please help me? Thanks.
CDX
 
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Re: ADSR Integration

by antto on Wed May 28, 2014 5:18 pm

the VCA is controlled by 2 controll voltages which are added together
Roland have this sort of thing also in some of their drum synths

one of the control voltages is obviously the volume envelope, the other one comes from the accent circuit, that's what makes accented notes louder

i'm not good with electronics, so take what i say with a spoon of salt
the volume envelope (in its final form) comes out of Q31 and connects to both VCA chips (pin1 if you use BA662, or thru Q3,4,2,1 to pin1 if you use BA6110)
the other envelope (from the accent) is added at that same spot, coming from D27

so, to replace the volume envelope with your ADSR - i guess.. lift Q31's leg there and hack-in your signal somehow
i don't know what kind of voltages are there, so you probably have to poke with multimeters/scopes and see what's going on, so you don't blow up something

the gate into the volume envelope comes via D35 (the gate-OUT on the rear panel comes from D34)
again, check what kind of voltages are going on and what your ADSR expects..

i think there's also useful info in the wiki, and i think maybe someone already did an ADSR mod, but i think it was for the filter

antto
 
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Re: ADSR Integration

by CDX on Thu May 29, 2014 12:09 am

Thanks man! I'll check it out and update the result.
CDX
 
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Re: ADSR Integration

by altitude on Wed Jun 04, 2014 4:14 pm

Guest made a note on this way back when

http://www.ladyada.net/wiki/x0x/vcamods

altitude
 
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Please be positive and constructive with your questions and comments.