A cheaper and simpler alternative would be to connect the guitar to the audio shield's microphone input. Normally, that shouldn't work, but it finally does. Theory and practice...
I tried building a couple powered pre-amp/buffers using a JFET and op-amp to try and match impedance etc, but have not had much luck in getting a good signal. Running the guitar output directly into the mic-in and fiddling with the gain gives a surprisingly good result. Will have to experiment with the line-in gain as mentioned. Thanks for the suggestions!
Try the line-in input.
The datasheet shows that SGTL5000 has 29K input impedance on line-in while the mic-in has 2.9K.
Line-in it's match closely the guitar impedance and will give better results.
Does anyone have a simple pre-amp or buffer circuit to allow the input of an electric guitar signal to the Audio Shield line-in?
Somehow when I read the datasheet I saw 100kOhms, ....now when I read it, it says 29kOhms (parallel universe??)