Indeed, bad jacks were mentioned in post 2! I forgot about that once I hopped down the rabbit hole. "Rectification" is a pretty darn good way of describing what I was hearing. Once I noticed the threshold behavior I was reminded of something I read somewhere about oxidation creating a diode, either in the context of DIY AM radios, or in TUT, or probably both, and that helped tip me off that it might be the jack(s). Maybe I should save the bad jack and make a radio with it. 
Thanks for the input and help!

Thanks for the input and help!


