Envelope Generators and Voltage Controlled Amplifiers

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JingleJoe

Joined Jul 23, 2011
186
The latest project I've been working on is a simple synthesizer, I don't know why I allways feel the need to keep my projects secret, perhaps it stems from being a mad scientist?
Anyways I wanted to get some help, opinions and knowledge from you chaps regarding envelope generators and voltage controlled amplifiers. Primarily the envelope generators.


Somewhere online I found this circuit (typically I can't find the website now)
simple_envelope.jpg
It looks so nice and simpl but it didn't work in simulation. Can anyone explain why? Is the circuit wrong or is my simulation software just not working?
I spent hours faffing around with capacitors and resistors trying to make it work, but didn't get very far.


In the end I came up with something based on a 555 timer monostable circuit which works in theory. At which point I was thinking "Why did I even consider using any other IC?"

555env-jpg.jpg(circled numbers are pins of 555 timer chip)

Taking the voltage from the capacitor (with a voltage follower) I should be able to get those shapes. Do you chaps think this will work too? Do you think my trigger input circuit will function correctly; making the monostable circuit trigger on the rising edge of the input pulse?
Just thought, I could take the diode in series with R3 and connect it directly to +V allowing for very steep attack.

Any envelope generator circuits you chaps can suggest would be much appreciated.
 

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SgtWookie

Joined Jul 17, 2007
22,230
On the broader issue of sound synthesis; the famous SN76477N complex sound generator IC from the 70's is still available. It has a built-in ADSR section.
Gee, that's a rather amazing find! I would not count on them being available for long, as they have been out of production for quite some time. TI does not even list them on their site anymore.

I remember when Radio Shack carried those... darn, I'm old... :(
 
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