Concept for a guitar 'chopper' circuit

I’m looking for critique on a circuit I’ve been designing tonight. My friend has been wanting me to build this for a while, and as I’ve been teaching myself about electronics I just got to the point where I think I’ve figured out how to do it. Basically it’s just an effect that chops up the signal and makes it turn on and off rapidly.

The circuit uses an astable multivibrator based on the schematic here… In my version I took one of the outputs out (grounded the cap) as this will be the ‘off’ state for the signal. I also changed the caps to 10mdf as I have lots of them at home, and I chose 100K pots instead of the 15K resistors used in the original design. According to the formula given 0.693RC = (.0693) * (100,000) * (0.00001) = 693ms. Based on the desired effect it’s not likely he’ll ever need more than 500ms in each state so as long as my calculations are correct the RC combo should be what I need. I also inserted a bypass switch which is just a basic SPDT that shorts the tip of the input and output jacks together when up and connects the tip of the input jack into the circuit when down. The sleeve of the jacks are shorted directly.

So now I’m just wanting to hear from you guys that have much more experience and knowledge about this stuff than I do. Are there any glaring mistakes in this design that I’m missing? Will there be any signal issues when using this to switch audio on and off (pops, clicks, etc)? There’s obviously no power supply present in this design as I’m wanting to focus on the actual effect first, and considering I’m just using NPN transistors I’m not even sure if I need a regulated supply or if I can just use the 9V supply from the brick he’s already got on his board.

The schematic is here (in eagle format of course, my first time to use this program!)…

Just let me know what advice I can gleam from the gurus. Thanks in advance


You’re likely to find much more people with experience with this kind of circuits on