Griffin iPod Auto Charger - hissing sound

[howitts_done]

The AUX jack in the 2007 Mazda3 works great, so I thought I'd try the Griffin PowerJolt (http://www.griffintechnology.com/products/powerjolt/) to keep my iPod fully charged during my trips to work. As soon as I plug it into the 12 volt power supply (any of them), I get a 'hissing' sound from the speakers. The 'hissing' also changes pitch when I shift gears... How weird is that :loco

Needless to say I will be returning it tomorrow. Anyone have any thoughts as to why this might happen? Do you recommend another brand?

pros: Charges iPod, LED tells you when it's charged, includes a mini USB to charge while using iTrip or other docking device, USB cable, replaceable fuse

cons: Hissing sound, iPod doesn't turn off when car turns off (not sure if that is even possible. It is just annoying)

[CWP]

I just got a Belkin one at Best Buy. I'm not sure what model it is, but it has an aux-out on the actual charger part that sticks into the cigarette lighter. This makes a huge difference because you can plug the aux in line in the console right into the cigarette lighter adaptor. Mainly this means that the sounds is coming out of the dock connector and not the headphone jack, so the quality is far better. Also, you only have one cable to connect to the iPod. It was more expensive, $62 I think, but worth every penny. I think that Monster makes something similar but I couldn't find it.

[garboui]

sounds like you have some ground loop probs. there are three ways that you can tackle this.

1) dont use a charger while listning, ipods have crazy battery life as it is.

2) not the optimal soloution. get a ground loop isolator from rat shack. this goes inline with the audio signal and is basically a 1:1 line transformer. the problem with this is that theres lots of losses in signal as well as rolls off the lower frequencies alot.

3) tho most optimal solution that i have found was to get an isolated dc/dc converter. these can be a lil pricy but generally still cheaper than a GL isolator. what this does is acts as an isolating line transformer but for dc current. for charging an ipod a 6W model is sufficent and still allows for some headroom esp if running a fm transmitter from the ipod. the part that im using for my ipod setup is from digikey and was ~18. heres the link:
http://www.digikey.com/scripts/dksearch/dksus.dll?KeywordSearch?lang=en&site=CA&KeyWords=445-2489-ND&x=8&y=14
with this installed any hiss or ignition ticking i had was completly gone.