Back at post #42 there is a picture of a square wave, (not so square wave) and a comment about how bad it looks. The wave looks like this because it has just passed through a capacitor. (A high pass filter) (DC blocking capacitor)

What are you trying to do? Measure the output of your electric guitar in peak response mode?

For long before I was born, audio has been measured in two modes.

Average mode: Full wave rectify. Then use a 2hz low pass filter. The response time is set to about the spoken syllable rate. (half wave produces little error)

Peak mode: Full wave rectify. Use a filter with an attack time of 1.7mS and a decay time of 660mS. You need the 1.7mS attack time or any very small peak will peg you meter but you ear can not hear that small peak.

Do you want RMS response?