Improper grounding can cause weird noises. If the sound works fine indoors, then that might be the problem.
I am having some major audio problems with my mini in my car. While I do not have my in dash screen yet, I hooked everything up and used my 17" flat panel sitting on the passenger floorboard.
Here is a quick down and dirty of the setup.
1.42Ghz Mac mini (256RAM, 80GB) stock from my local Apple store.
2005 Hondac Civic Hybrid with the *stock* factory cd player....that is hooked up to a HOM98-AUX PIE adaptor to give me RCA preouts.
The preouts plug into a Soundbridge AUX3 which splits the preout and give me 3 powered preouts that is controlled via a dash mounted rocker type switch.
I have my XM radio hooked up to one the main preout....my iPod hooked up to preoutA and nothing hooked up to preoutB. (preoutB is where I plan on hooking the mini up to). To save a little time I unplugged the plug from the back of my iPod dock (which is plugged into preoutA) and plugged it into the headphone out of the mini.
All of a sudden I get this horribly loud hissing sound and can barely hear any audio at all.....hmm. The iPod when plugged in with this cable plays flawless....however when switching the plug into the mini hissing...
I figured that *maybe* the mini wasn't giving me a good quality audio output so I headed over to my local CompUsa and purchased a Griffin iMic. (even though the preout is powered by the Soundbridge AUX3).
I then hooked up the iMic to the mini and then to preoutA....same results. Very lound hissing and very poor low audio out of the mini. I tried hooking up the iMic a few different ways??? Always with the same results.
can anyone help me out maybe as this is driving me nuts....
kris -at- aperturefoto.com
Sounds like dirty power to me too, check it inside and if its still crap there are a few things you can do. I would suggest some kind of power regulator/cleaner to go with the inverter you are running.
Alternatively it might be the LCD badly reacting to the dirty power - turn it off in the car/ get rid of the power board.
Confirm line out on Mac mini works fine (is it volume up most of the way?)
Remove other 240v devices from the inverter
Get cleaner power if problem persists.
Alternatively you can pull a dodgy hack * I DO NOT RECCOMEND THIS UNLESS YOU KNOW WHAT YOU ARE DOING * remove the earth and see if the audio is still crap. You should not use this as a perminant solution but more a method for figuring out what is wrong.
Be aware that if the mini goes "live" you might be providing the fastest root to ground. Which will hurt a lot.