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[on:]

Hey, y'all.

I'm working on a guitar tuner, and I've just finished building an op-amp that will amplify the signal from the guitar to a range that the Arduino can read. The only thing left to do is offset the signal such that the entire signal is positive so the analog pins can read it. What I've been trying to do is use the 5V and GND from the arduino in combination with another op amp to add 2.5V to my amplified guitar signal. Unfortunately, I think the grounds are interfering with each other to some degree. Connecting them completely kills the output signal. Any suggestions?

[edit]: I posted a picture of the op amp I've constructed a couple posts down.

[edit2] Based on some outputs from feeding the amplified signal into some random attempts at adding the offset, I hooked the output into a zero level detector with a capacitor in between, and it's created a signal that generates impulses at the fundamental frequency of the note being played. Awesome, no?

[Reply #1 on:]

Can you sketch your circuit?

[Reply #2 on:]

Here is the op amp  I currently have constructed.