OK, so I worked with NAD support on this and they thought it might be a hardware issue and recommended swapping out for a replacement unit, which I was able to do because I was still within the return period. Tested with replacement unit and the popping persists.
Thinking there is in fact nothing wrong with the NAD, I was curious whether this might be an issue with some of my other digital playback devices. So I tested literally every other digital playback device I own, including 2019 Intel Macbook Pro (which I use with a Schitt Modi 3 DAC), 2024 M3 Macbook Air, a couple of older Intel macs, and I was able to replicate the popping in every single playback device using the same track in either Amazon Music or Tidal. I mainly used Salnotes Zero 2 IEM as the output device but also a KEF Q150 for my desktop setup (the MBP with the Schitt Modi), and a pair of small Audioengine powered (active?) speakers I pulled out from storage, and the popping persisted no mater what the output device.
So now I'm guessing this is just something that happens when you try to scan within a digital track and that I am hyper sensitive to something most folks tend to ignore. For example, if you load the track linked below and just jump around from place to place within the track, I am betting you'll hear small popping sounds at least 50% of the time (because otherwise that would mean somehow all of my devices and speakers share the same defect which is not likely). And for whatever reason the popping happens more frequently or is more noticeable for some tracks as opposed to others, so your results may vary for other tracks, but I was able to replicate the popping pretty reliably across all my devices with the track below. If anyone has Tidal or Amazon Music, would love it if they can try and reply back here. Thanks!
[Amazon Music] https://music.amazon.com/albums/B002R9H8T8?trackAsin=B002R9MUZK&ref=dm_sh_2851-7176-7c4c-79a4-a5bb0
[Tidal] https://tidal.com/browse/track/70432916?u
