I had the popping and clicking issue once so far in a good week's use with the iPhone 4. I just switched it off and on again and it stopped. It doesn't appear related to processor or memory incidentally, as I have a jailbroken device and freed-up both to no avail: a restart alone will fix this.
Ah- interesting to know that it works with jailbroken devices. I've yet to do that, but might consider it with my iPod since it's not my phone and I pretty much use it as a dedicated music player. In other words, it's not the end of the world if I brick it or lose contents. I think I also might wait a while before doing the iOS5 upgrade on this- just to make sure. I'm pretty certain that iDevice protocol is pretty strict, but I also know that these kinds of devices (well, just the handful so far) are probably 0.00001% of iDevice users. So I'll take the "you first" approach for now. 
This is yet another DAC that proves to me the much more 'real' sound of minimum-phase filters as opposed to linear-phase filters. Filter 1 is much more 'smeared' than filter two. Of course, it compliments some music more, but in the time domain it's a long way behind. The phase problems of a well-designed minimum-phase filter only rise above a few samples of discrepancy as the audio frequency goes above 14kHz — the point around which human hearing can't really determine differences in pitch. It's more like noise up there really, we're not that sensitive to a few samples of phase!
It sounds like your ears are much better trained than mine because I have a hard time telling the difference between the two filters. If you don't mind my asking, can you give me an idea of what you look for, what kind of musical material best reveals the differences, and what parts of that material are most revealing (soft passages, high freq, etc.)? Thanks!
, it's more than enough...
