AR envelope generator


Posted on Feb 4, 2014

By no means is this a necessary addition to the benjolin but its one I`ve had some fun playing with and decided to add to my Modular Benjolin design. This circuit is a dual Attack/Release envelope generator. The AR is especially useful when combined with the modular rungle bit output mod. This is a very simple design and is easy to build and use.


 AR envelope generator
Click here to download the full size of the above Circuit.

It is also relatively easy to modify for other applications. You could definitely get by with one but its such a low part count and required just one IC so I decided to build two. R5 and R6 creates a voltage divider that sets your threshold voltage which has been set at around 2. 5volts. Any incoming voltage above 2. 5 volts will trigger the comparator and set the output high (which is 9 volts for this circuit). This is a simple RC (resistor capacitor) slope generator. The rate of attack and decay are determined by the two potentiometers and the capacitor (C1 for AR1 and C2 for AR2). R7 and R8 act as peak limiters. The voltage coming out of the op amps (pin 1 and 14) is an envelope that swings between the power rails (+9VDC and -9VDC). In actuality it will swing just below +9VDC and above 9VDC. If you want a bipolar envelope then leave out the offset. I want the base voltage to be exactly 0 volts so I installed a trim pot to the positive power supply. I use this to pull up the negative swing of the envelope until it is exactly 0 volts. It will take some fine adjustment. An oscilloscope will make it a lot easier but isn`t totally necessary. One way to test without a scope is to plug the output of the AR generator into the CV input of a VCO (like one of the ones on the benjolin). Make sure the AR is not being triggered. Unplug the connection to the VCO CV in and make a note of the pitch. Plug it back in and adjust the offset...




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