Problem: EMI-Like noise when playing Fuze connected to USB car charger

SanDisk MP3 players Sansa® Fuze™
1

I’ve had my 4GB v1 Fuze for about 7 weeks and love it. I take it with me everywhere (well, almost everywhere :wink:).

When I connect the sync/charge cable to a USB car charger plugged into a cigarette lighter in my car, then connect the audio cable from the headphone jack to the aux input jack on my car’s head unit, I get a very annoying buzzing/humming sound (kind of like EMI interference) out of my speakers. The sound completely overrides any audio playing on the Fuze – no music can be heard. I’ve tried to isolate the problem with some basic troubleshooting. Here’s what I’ve found:

1. Fuze running on internal battery connected to headphones – plays normally
2. Fuze connected to USB car charger with key turned off and audio through headphones – plays normally
3. Fuze connected to USB car charger with key powering accessories only and audio through headphones – plays normally
4. Fuze connected to USB car charger with ignition turned on and audio through headphones – plays normally
5. Fuze running on internal battery and audio through aux input on car’s head unit – plays normally assuming the car is turned on to provide power to drive the head unit
6. Fuze connected to USB car charger with key turned off and audio through aux input on car’s head unit – no sound because no power to drive the head unit
7. Fuze connected to USB car charger with key powering accessories only and audio through aux input on car’s head unit – EMI-like sound produced
8. Fuze connected to USB car charger with ignition turned on and audio through aux input on car’s head unit – EMI-like sound produced.

Additional information:
1. In scenarios #7 and 8, trying to adust the volume by turning the volume wheel on the Fuze has no effect on the volume of the noise. However, trying to adjust the volume by adjusting the volume on the head unit does affect the volume of the noise.

2. In scenarios #7 and 8, the EMI-like sound is produced whether the file on the Fuze is playing or is paused.

3. My car has 2 cigarette lighters. This phenomenon occurs with both of them.


4. I have 2 USB car chargers. This phenomenon occurs with both of them.

5. I have tried several cables. This phenomenon occurs with all of them.

5. I also have a first-generation 4GB Clip that experiences the same phenomenon.

So, basically, I can recharge one device (say my Fuze) with the USB car charger while playing the other (say my Clip) on its internal battery through the head unit’s aux input (scenario #5). The battery life has never presented a problem for me running out of tunes to play on the road. But, I would still like to have the option of powering my Fuze through the USB car charger while listening to it through my car’s head unit.

Any thoughts and ideas would be appreciated. Thanks.

2

I had the same problem.  I have an internal FM Modulator wired directly into my FM head unit with a 4.5mm plug that I plug my unit in, and whenever the USB car charger was connected, I would get terrible ground loop noise.

I actually had to go in and replace the 4.5mm plug cable that plugs into the FM modulator with ones that had ferrite cores in the cord.   The FM Modulator had RCA to RCA cables that had ferrite cores on them.  By adding those “extensions” to the RCA inputs, it eliminated the problem for me. 

Sounds like you have a similar issue.  You are picking up ground loop noise.  Short of modifying the aux jack to provide ground loop isolation,  the only thing I can think of short of rewiring your aux in, is to run the unit on internal battery while driving and then charging when you are parked, or make a habit of charging more often. 

I play my Fuze at work, and it’s always topping off. 

3

Thanks for your posting, p_opus. It’s not a critical problem because, as you suggested, I’ve just been running the Fuze on its internal battery when listening to it in the car. Since I rarely drive more than 2 or 3 hours a day, the battery has never run down. Even if it did, I have a Clip and a couple of USB Flash Drives I can listen to while the Fuze is recharging.

I guess I’m just the kind of guy that likes things to work the way they’re supposed to work. And when they don’t, I like to find out why, and fix the problem if possible. But, in the overall scheme of things, this is a minor issue. One that I can certainly live with.

Thanks again for your comments.