Aux/usb noise

[paulb07]

Just fitted aux cable from in car tunes wrapped in aluminium tape from maplin,works perfectly with no interference at all I also got a usb charger http://www.amazon.co.uk/gp/product/B002ATMN22?tag=5336653588-21 so i can charge and play my ipod at the same time.Problem is when i plug it into the lighter socket whilst playing the ipod there's a loud buzzing noise.I thought it may be interference from the alternator but the noise stays the same whilst accelerating.Annoying as both work fine on there own just can't charge and play at the same time.Anyone have the solution to this problem?

 

[bcworkz]

The problem is most likely that the conversion from lighter 12v to USB 5v is done via switched mode. The output from switching is typically very noisy, and needs proper filtering to avoid the noise you are hearing. This is not the same as EMI, so the shielding of the input cable doesn't help. A better filtered adapter may help, but since batteries don't care about noise, I'm not sure filtering is a priority in any product.

A linear mode conversion (wound transformer) should be less noisy, but you could still get noise from related cheap electronics, so there may be no real benefit. The car already has USB compatible 5v DC to power computers, I don't know how clean it is. This solution would require some sleuthing and a custom USB cable.

I can't guarantee a noise free solution even exists, but I am 90% sure this is the source of your noise.

 

[wegras]

Just fitted aux cable from in car tunes wrapped in aluminium tape from maplin,works perfectly with no interference at all I also got a usb charger http://www.amazon.co.uk/gp/product/B002ATMN22?tag=5336653588-21 so i can charge and play my ipod at the same time.Problem is when i plug it into the lighter socket whilst playing the ipod there's a loud buzzing noise.I thought it may be interference from the alternator but the noise stays the same whilst accelerating.Annoying as both work fine on there own just can't charge and play at the same time.Anyone have the solution to this problem?

Bluntly i think the price is the issue at £4.99 quality is not going to be high ( as below )
Cable looks similar to the one people buy for the 1 Series rather than the infamous BMW Y cable and invariable find them wanting

 

[paulb07]

I'll try the BMW cable and see if there's an improvement

 

[Liam-O]

my cable and usb cigar lighter cost less then £5 together and i do not have the noise you describe

 

[paulb07]

just tried it in my van and there's only a very slight noise you can only just hear so i don't think it's the cable, more something to do with the lighter socket.