Noise through Ipod in Car (Not Alternator)

[Strat]

Hi guys. Having a bit of an issue with my Ipod Car setup.

I have a 20gb 3G using Sik Imp adaptors for power and line out. These go directly into an Amp that is driving my speakers. The amp is connected directly to the car battery using proper thick Amp wire. Fused etc etc.

I am having this problem when the car's ignition is in the ACC position (no engine/alternator running) aswell as when the car is on.

When the Firewire port is plugged into the Sik car charger I get a constant click/hiss sound through the speakers, that gets worse as the volume on the amp is turned up. When the Ipod isn't plugged into the charger it is crystal clear.

I tried plugging it in through the charger hooked up to an external power source (A car battery charger) and it was also crystal clear.

I tried plugging it into the amp power instead of through the cigarette lighter and again it was filled with static and noise.

I don't mind running it straight to the battery if need be but I'm not sure if it will help. Perhaps I need an isolater or a few capacitors or something??

Anyone got any ideas. Finding it really annoying :)

Thanks guys.

(If you need more explanation just let me know.)

[oink1]

If the iPod's line out is feeding straight to the amp,whats controlling the volume level?

*edit* - Thinking about it perhaps it's the charger making noise being picked up by the line out and then being made worse as it's amplified... the more i think about it the more it makes sense - the charger must have some sort of regulator/rectifier circuit thats causing the interferance.

*edit2* - There again you say the setup works fine using the charger with an external power source so it's a wierd one...

[Strat]

The amp has a volume control, that I removed and mounted externally on the dashboard.

I thought it was the charger making noise at first but it doesn't do it when it's plugged into an external power source (charger running off a 240V AC --> 12V DC adaptor)

[oink1]

Originally posted by Strat
The amp has a volume control, that I removed and mounted externally on the dashboard.

I thought it was the charger making noise at first but it doesn't do it when it's plugged into an external power source (charger running off a 240V AC --> 12V DC adaptor)

Yeah - see edit2 :p

*edit* - now you've said you have 'modded' the volume controll,have you exhausted that as a possible cause? - it must have a large run of wire acting like an ariel - ripe for picking up any possible interferance...

[oink1]

And as for it not making noise when using the external power,you take the cars electrics out of the equation then so IF it's the culprit theres no chance of it feeding back to the amp therefore no noise...

[Strat]

Yeah definetly not that. Works fine with my portable CD player. And fine with the ipod not charging, so the volume control is out of the question.

At the moment I am thinking one of these would help

5 Amp Car Noise Filter (http://www1.jaycar.com.au/productView.asp?ID=AA3072&CATID=&keywords=aa3072&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=)

or

Car Stereo Line Isolation Transformer (http://www1.jaycar.com.au/productView.asp?ID=AA3085&CATID=&keywords=aa3085&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=)

But I am not sure what the differences are or which one if either would help.

I assume the Isolation transformer would plugin between the ipod and the amp? Where the noise filter would plugin between the cigarette lighter and the charger?

EDIT: It is definetly an issue with the car electronics. Interferance from something in the car, or the amp or something else. But I am not sure how to go about fixing it.

[oink1]

the filter you'd have to wire to the back of your ciggy lighter and the transformer would go between iPod and amp but both of these are for stopping alternator noise,and we know thats not the problem as it's happening wether the engine is running or not...

[oink1]

Presumably the volume pot was grounded in the amp somewhere when it was mounted internally - is it still now?

[Strat]

Yep still grounded :)

[GloomyYardGnome]

I had a similar problem with my ghetto-rigged car setup (although it does look kick ###).

I just turned down the sterio volume knob and turned up the iPod volume knob. It makes a big difference.

If you think its the wires picking up interference, just wrap them in some copepr mesh.

[n3tfury]

you didn't mention in your original post how/where your amp is grounded.