I have an AG 15 Acoustic Guitar Amp, this one right here:

Now I've decided recently I want to build this:

And I want to mod it a bit to have a mono output jack on it so I can plug it into my amp.
I don't know how much everyone here knows about circuitry and whatnot, but would plugging this thing into my amp cause any problems for the amp due to things such as impedance or high voltages? (I really don't know if 9V for input is too much or not.)
im not familiar with theramins. but 9V output isnt too much. impedience shouldnt matter on the input stage too much. and its an acoustic amp so its designed to handle line level instruments and stay clean.
If you don't talk to your kids about GAS, who will?