Hi
I want to build a guitar effect pedal using a Teensy 4 and the Audio Shield. I have built many analog effect pedals and understnad the need for a high impedance buffer / preamp and for keeping analog and digital signals and supplies separated. What I don't know is what signal levels are OK with the SGTL5000 and how I should protect it against input voltages that would damage it. I looked in the SGTL5000 datasheet but couldn't really find an answer. Some guitar pickups (and guitar effect pedals) can have quite high output voltages (7V peak-to-peak for some active pickups) which I guess could harm the codec. Is there a recommended way to protect the codec - and is it needed or is there already some protective circuit inside the SGTL5000? Clipping the signal with diodes to ground and audio is an easy solution, but will still allow a big voltage swing due to the forward voltage of the diodes. Would that work or can you recommend some other solution?
I have looked at blackaddrs guitar audio shield, and it uses a diode clipping setup, but it also uses another codec (WM8731) that might be different with regards to protection/voltages.
Best regards
/MJ
I want to build a guitar effect pedal using a Teensy 4 and the Audio Shield. I have built many analog effect pedals and understnad the need for a high impedance buffer / preamp and for keeping analog and digital signals and supplies separated. What I don't know is what signal levels are OK with the SGTL5000 and how I should protect it against input voltages that would damage it. I looked in the SGTL5000 datasheet but couldn't really find an answer. Some guitar pickups (and guitar effect pedals) can have quite high output voltages (7V peak-to-peak for some active pickups) which I guess could harm the codec. Is there a recommended way to protect the codec - and is it needed or is there already some protective circuit inside the SGTL5000? Clipping the signal with diodes to ground and audio is an easy solution, but will still allow a big voltage swing due to the forward voltage of the diodes. Would that work or can you recommend some other solution?
I have looked at blackaddrs guitar audio shield, and it uses a diode clipping setup, but it also uses another codec (WM8731) that might be different with regards to protection/voltages.
Best regards
/MJ