[sdiy] simple and effective ADSR circuit using ICs

[Scott Gravenhorst]

I've got one that uses a 2 ICs: a 4069UB (!!!), a dual opamp and some diodes. 
There are no discrete transistors used.  I've not seen this design before, so it
might be mine!

http://home1.gte.net/res0658s/fatman/ADSR.html

The top schematic has been tested and works.  The middle one is not yet tested
and contains 2 improvements, the threshold for end of attack is raised to a
higher level (2/3 Vcc instead of 1/2 Vcc) and there is a "punch" switch added.

Note that the power supply spec'd for the 4069UB is +8 volts (because this was
designed for use in a FatMan), but I see no reason it couldn't be used with +15
volts (as well as powering the opamp from +/-15 instead of +8/-12).  The output
amp could be tweaked for more envelope amplitude by changing the gain resistors.

The bottom schematic is something that a friend found on an OLD EFM site, but he
couldn't make it work as TomG had published it.  The original schematic had
critical errors and would not work.  I did the required troubleshooting and fixed
it for him.  The result of my work is represented in the bottom drawing.  The
circuit works as shown.  It does not, however, comply with the request for "no
transistors" and it also uses 3 IC packages.

synthplayer88 at spymac.com wrote:
>Hi guys,
>I was wondering if anyone can recommand any ADSR circuit build with only ICs and
>no transistors?
>
>I know it's possible to use two 555 timers triggered by the inverted oscillator
>signal to create an ADR envelope, the first attack setting can be varied through
>the voltage divider at the input of the first 555 and the timing RC can be used
>for dacay then the second 555 RC can be used for Release but what about sustain?
>
>thoughts?  
>

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-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
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