TomTom 910 - Hash Noise on Music

AVRHack2 · Occasional Visitor Joined: Dec 27, 2006 Posts: 24

Have a problem with the 910 playing music through the car radio - lots of electronic "hash" in the background. It's not noticeable most of the time, but on quiet bits it can be very irritating.

I've seen the other threads about ground loop isolators and I've fitted one, but it hasn't solved the problem - clearly mine wasn't a ground loop!

If I connect the same lead to my iPod - no noise at all. If I turn off the 910, no noise at all, so I've narrowed down to being generated by the 910 when it's "active".

However, before I fitted it in the car I plugged in some headphones directly to the 910's output and the sound was perfect - no hash whatsoever.

My guess therefore, is that it's probably because the FM modulator I'm using has a high impedance input, and this is allowing the hash to break across from PCB tracks carrying digital signals in the TomTom, whereas with headphones plugged in, as these are only 120 ohm impedance they will effectively short out any high impedance sources. Or this is what I'm hoping, or I'm stuck with the noise!

I'll prove this one way or the other in the next few days by bunging a couple of 100 ohm resistors across the TomTom output in the connecting lead.

Anyone else had this problem and if so, what was your solution?

limans75 · Occasional Visitor Joined: Mar 14, 2006 Posts: 41

Hi there,

I too am having the same problem, I bought a Belkin FM transmitter in the absence of the TomTom Car Connect module. Depsite playing around with different radio frequencies I still get the "hash" sound. I wont pretend to know anything about impedence and ohms but would like to know if you manage to find a solution to the problem.

I was woundering if IPods have the same problem and you have answered the question, so it must be something to do with the TomTom.

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