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 Forum index » DIY Hardware and Software » Ken Stone designs - CGS
CGS116 problem, sustain portion is producing low voltage
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Argitoth



Joined: Jun 24, 2008
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PostPosted: Sat Jul 06, 2013 8:54 pm    Post subject: CGS116 problem, sustain portion is producing low voltage Reply with quote  Mark this post and the followings unread

This is very strange, no idea if this recently happened or I finally noticed it. Is the sustain portion of the CGS116 supposed to be noticeably lower in voltage than the attack portion?

What I mean is that if I put the edit:DECAY to 100% and sustain to 0% I get a nice high voltage. When I put edit:DECAY to 0% and sustain to 100%, the sustain voltage cannot open my filter nearly as much. That renders the sustain portion not very useful Sad

This is my favorite ADSR otherwise... very disappointing that the sustain ain't right.

Last edited by Argitoth on Mon Jul 08, 2013 11:39 am; edited 1 time in total
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andrewF



Joined: Dec 29, 2006
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PostPosted: Mon Jul 08, 2013 7:07 am    Post subject: Reply with quote  Mark this post and the followings unread

Argitoth! its been so long!
Do you have a scope to look out the output, its the best way to know what is happening.
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Argitoth



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PostPosted: Mon Jul 08, 2013 10:10 am    Post subject: Reply with quote  Mark this post and the followings unread

andrewF, sorry no I don't have an oscilloscope. I didn't match my transistors, is that to blame?
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Argitoth



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PostPosted: Mon Jul 08, 2013 11:38 am    Post subject: Reply with quote  Mark this post and the followings unread

Oh no, it's not the attack that should be set to 100%, it's the decay. The decay at 100% effectively sustains the voltage for a while. However, when the decay portion is over and goes to the sustain portion, the voltage can never be nearly as high as the decay portion. 0% attack, voltage rises, 100% decay, voltage slowly drops, 100% sustain, voltage drops to some low undesirable amount.
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roglok



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PostPosted: Mon Jul 15, 2013 11:18 am    Post subject: Reply with quote  Mark this post and the followings unread

what kind of signal are you using to trigger the envelope?

the sustain voltage of an ADSR envelope is held high as long as there is a gate present (e.g. generated by holding a key on a keyboard). if you are instead using only a short trigger, the sustain phase is very short as well.

not sure if this is related to what you are experiencing...
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Argitoth



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PostPosted: Mon Jul 15, 2013 12:02 pm    Post subject: Reply with quote  Mark this post and the followings unread

Here's a demo. I am triggering the envelope with an oscillator square wave. The envelope out is going to a resonant filter. You are hearing the filter output. You will notice the first 2 oscillations go "pop wooo" which is the sustain failing to keep the voltage high after the decay phase. The next two examples I increase the decay time to show you how high the voltage CAN be. The decay portion is long enough that the sustain portion is not audible because the decay is set to a long time.


cgs116_sustain_problem.mp3
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Argitoth



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PostPosted: Thu Jul 18, 2013 4:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

Here's another clue: I can get the sustain level to an acceptably high voltage via its sustain voltage control input with a DC offset voltage.
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