I installed a Dectet between between the wall and my PPP. Now the THD has increased to 5+(input) to 1.4+(output). Prior to install it was and Input or 3+, ouput of 0.8-0.9. Is this normal?
No, not at all. Are you sure? Have you checked that the connecting cables are working right? Maybe swap them around and also make sure the voltage on the input remains the same with and without the Dectet. I have never heard of anything like this under normal conditions and even if it was defective, I can’t imagine what it could possibly due to make the distortion go higher.