Envelope Generators and Voltage Controlled Amplifiers

Discussion in 'The Projects Forum' started by JingleJoe, Aug 14, 2011.

  1. JingleJoe

    Thread Starter Member

    Jul 23, 2011
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    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.
     
    Last edited: Aug 15, 2011
  2. bertus

    Administrator

    Apr 5, 2008
    15,647
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    Hello,

    Perhaps this old schematic might bring you on idea's.
    See attached PDF.

    Bertus
     
  3. JingleJoe

    Thread Starter Member

    Jul 23, 2011
    185
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    That's marvelous thankyou :)
     
  4. KJ6EAD

    Senior Member

    Apr 30, 2011
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    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.

    http://en.wikipedia.org/wiki/SN76477
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    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... :(
     
  6. KJ6EAD

    Senior Member

    Apr 30, 2011
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  7. bertus

    Administrator

    Apr 5, 2008
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  8. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    I bought one from Radio Shack! Probably around '78 or '79.

    The sad thing is that I've probably still got it, kicking around in my junbox somewhere... ;)
     
  9. JingleJoe

    Thread Starter Member

    Jul 23, 2011
    185
    10
    I will buy it from you!

    Thanks for the tips too chaps :D
     
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