Just an observation, not a definitive statement from an expert, but a few interesting facts fell in to place for me this morning.

I have been running my Ipod through the Aux port on the advanced audio system, and I love it. I have read loads of posts about Ipods not liking the vibrations (the large capacity Ipods anyway), popping noises in the stereo system and also the disappointment in sound quality with the standard helmet speakers. None of these seemed to apply to me.

Anyway, as my PDA can play music easily enough I decided to get a 16Gb memory card and use that rather than run the risk of damaging the Ipod. Today I rode in to work and guess what...sound quality not great and popping sounds. Interesting thing is that the music I uploaded to the phone is the same as that on my Ipod. Clearly an MP3 player is not an MP3 player is not an MP3 player. Sounds like a silly statement and one that I would, ordinarily, have raised my eyebrows to. It is a digital file format, what could go wrong?? My initial thoughts as to why pay more for an expensive MP3 were 2 fold, unfortunately the first being the "brand pose value", the second being the much improved user interface you get with the more expensive products. Now I believe there is actually a quality of sound difference as well.

Based on this experience, if you are experiencing popping through an MP3 player, try an Ipod and see if there is a difference. Maybe we throw stones at HD too readily at times

 

Maybe if you install a sert on your MP3 you can get away from the lean pop.

 

Check your cable connector on both ends. I had a similar "pop" while using my Ipod-Nano. I noticed that the jack on the end of the cable was slightly worn and was not providing a good tight fir or click when engaged. When I bought a shorter cable...tada!
Try a different cable.

 

interesting...

 

I also have found the sound quality of an iPod (nano) was much better than my PDA.
With the 1000 capacity on a 4 gig unit it seems to be enough for any long ride. I mean 1000 songs is a lot of music. I did have the poping noise as well. I found that using the plug that curves right out of the jack worked best. it fits snug against the stereo. I did have shoten the cable from 3 ft to 8 or so inches. All in all there are many ways to carry music with you. The nano is the way I went do to the fact that it is not a hard drive. Just my two cents.