I built a gain clone amp based on the LM3886 that I found on circuitbasics.com and it sounds really good. But I'm struggling with how to calculate the input impedance. I'm making a preamp for the project and I'm trying to make sure the two stages are close enough. I've scoured the datasheet but TI doesn't give an explicit value. They show a typical application circuit, which the fine folks at circuitbasics.com based their design on. And they give a short explanation about how Rin relates but the I'm not sure how to interpret their explanation. To make it more confusing, circuitbasics.com added some input filtering to set the bandwidth and it seems like that could be impacting the impedance as well.
And something else that I find confusing...TI says in their notes that the input impedance is determined by Rin but I've read over and over again that op amps are designed with very high input impedances (>1M) in order to keep the current very low.
I could really use some help sorting the wheat from the chaff!