|The output buffer has a built in one diode voltage subtractor so that the output falls very close to zero at rest. TL082 is powered by FatMan type supply (+8v / -12v). Output can be expected to be around 6.6 volts at attack peak, this is approximately the same as the FatMan's built in ADSR. The CD4069UB is powered by 8v and ground. A 10K pot from the OUTPUT to ground can be added for adjusting the level of output.|
Originally, this design came from one of Tom Gamble's EFM projects (I think). This drawing has several corrections to the original and has some other design differences.
The ADSR output goes from 0 to about 6.5 volts (consistent with the FatMan's ADSR). The actual output level can be changed by changing the value of the OpAmp's feedback (6.8K) resistor. A larger value giving more gain.
I strongly recommend using a CMOS version of the 555. ICM7555 is one of several equivalents.
Since the opamp spec'd is a dual, you could add an inverted output.