using sansa clip+ in car

[arek00]

i have a problem with my sansa clip+ in my car. below my test configurations:

1. ac charger >> sansa >> car radio = ok
2. car charger >> sansa >> phones = ok
3. car charger >> sansa >> radio = there is no sound after connect charger and sound is back after disconnecting

can you check that you have the same? any ideas how to fix it?

[saratoga]

You may have a ground loop due to how your stereo is wired (basically power flowing through the headphone to the stereo and then through that to the battery).  I'm not sure what the best way to solve it would be. 

[TurboZutek]

This can be solved very easily. You must remove the GROUND connection on your car charger, the easiest way is to cover the two prongs at either side of the cigarette lighter jack in black electrical tape and leave the centre pin in place.

Everything will start working then.

Chris...

[saratoga]

You must remove the GROUND connection on your car charger, the easiest way is to cover the two prongs at either side of the cigarette lighter jack in black electrical tape and leave the centre pin in place.

Since the ground in this case would be the negative terminal of the battery, doing that would be equivalent to unplugging the player.  That will obviously prevent a ground loop, but will also mean that he won't be able to use the charger.

[TurboZutek]

The signal ground for the Audio will become the ground for the charger and the amplifier in the CLIP+ will stop ground-loop oscillating.

I know it works because my car is hooked up that way right now. You can test this theory by running the player, plugged into the charger by USB and then just touch the ground connection on the charger to the ground ring of the cigarette socket; instantly the audio dies.

Bizarre design flaw in the CLIP+ and an even weirder workaround, but I've been using the player this way for several months now, no damage to the player or the head unit.

/Try it

Chris...

[saratoga]

The signal ground for the Audio will become the ground for the charger and the amplifier in the CLIP+ will stop ground-loop oscillating.

The problem with this reasoning is that the clip+ headphone ground isn't actually connected to the power ground.  Its hooked up to an active common ground which is biased above power ground.  Looking at the datasheet it apparently has an overcurrent protection that kicks in at 300mA, so presumably a current under that won't damage it, but I'm not sure I would recommend trying this.  You certainly risk burning out the player's amplifier by driving quite a lot of current through it.

I know it works because my car is hooked up that way right now. You can test this theory by running the player, plugged into the charger by USB and then just touch the ground connection on the charger to the ground ring of the cigarette socket; instantly the audio dies.

Thats probably the overcurrent protection kicking in to prevent you from blowing up the amp.  Did you actually try charging the clip+ that way, or was this with a different player?

Bizarre design flaw in the CLIP+ and an even weirder workaround, but I've been using the player this way for several months now, no damage to the player or the head unit.

A ground loop generally happens because the stereo is wired up properly to the car battery.

[yapper]

It would probably be better to use a ground loop isolator on the audio output and leave the player powered properly.

[TurboZutek]

The problem with this reasoning is that the clip+ headphone ground isn't actually connected to the power ground.  Its hooked up to an active common ground which is biased above power ground.  Looking at the datasheet it apparently has an overcurrent protection that kicks in at 300mA, so presumably a current under that won't damage it, but I'm not sure I would recommend trying this.  You certainly risk burning out the player's amplifier by driving quite a lot of current through it.

Yeah, that's pretty much what I thought when I tried this, however the player when charging draws no more than 100ma, even at close to max volume while playing. The floating ground on my head units should be able to handle that OK. At that point I couldn't have cared less about damaging the CLIP+ because it wasn't working for my intended application (in car MP3) so I figured, what the hell: try it. 

Also, this unit doesn't get any hotter in the car than it does playing audio in my pocket. It doesn't seem stressed.

Thats probably the overcurrent protection kicking in to prevent you from blowing up the amp.  Did you actually try charging the clip+ that way, or was this with a different player?

No everything I'm talking about here was with the CLIP+: I don't have any problems like this with my other AUX connected stuff.

Why would there be an over-current when the player is being charged from USB?  It charges and plays fine when powered from a laptop with USB that's separate from the car, just not while output and power are connected to the same car.

I've charged the CLIP+ like this (with p/gnd disconnected) for several months now and listened to it in car while it's running with no problems at all. If it's over-current protection, it's not very good because the player will still function and play, but the audio sounds like mince while there are two grounds connected.

And what good is a design that overcurrents when it's correctly connected anyway? Lol! 

A ground loop generally happens because the stereo is wired up properly to the car battery.

I get that, but the earthing system on all my cars are A1 and the player will behave this way in all of them: all of the head units are OEM factory installs and the wiring hasn't been changed at all from stock. No big amps or upgraded speakers.

I have several other players and smart-phones that I run off the same chargers and into the same stereos in the same cars and they all behave perfectly. Only the CLIP+ that acts up in this way.

If there's a safer way to get this to work, I'm willing to experiment and try anything you can suggest in the name of getting an answer to this question, as it's clearly affecting a few people. RockBox is awesome and the CLIP is a sweet little player (and cheap), so I'd love to know why it won't play nice with my cars!

It would probably be better to use a ground loop isolator on the audio output and leave the player powered properly.

Already tried using this:

http://www.ebay.co.uk/itm/3-5mm-Earphone-Jack-Ground-Loop-Isolator-Noise-Filter-/280615811526?pt=UK_In_Car_Technology&hash=item41560179c6

Still no audio with two grounds. 

It's weird, hey?

Chris...

[saratoga]

Why would there be an over-current when the player is being charged from USB? 

Assuming the USB you mention here is still the DC adapter you mentioned above, its because your stereo isn't wired right and voltage between the AUX jack and the car's ground that pushes enough current to trigger the overcurrent protection.

It charges and plays fine when powered from a laptop with USB that's separate from the car, just not while output and power are connected to the same car.

Thats not surprising, there would be no ground loop in such a case. 

I've charged the CLIP+ like this (with p/gnd disconnected) for several months now and listened to it in car while it's running with no problems at all. If it's over-current protection, it's not very good because the player will still function and play, but the audio sounds like mince while there are two grounds connected.

And what good is a design that overcurrents when it's correctly connected anyway? Lol! 

The purpose of overcurrent protection is to keep you from melting your player by plugging into incorrectly wired stereos.  Since you launched enough current into the device to trigger the protection, and the player wasn't destroyed in the process, I would say its doing quite a lot of good.  Without it you'd might be looking for a new MP3 player and/or car stereo. 

A ground loop generally happens because the stereo is wired up properly to the car battery.

I get that, but the earthing system on all my cars are A1 and the player will behave this way in all of them: all of the head units are OEM factory installs and the wiring hasn't been changed at all from stock. No big amps or upgraded speakers.

A quick look on google suggests that ground loops are extremely common in car stereos, so I guess that is not surprising.

I have several other players and smart-phones that I run off the same chargers and into the same stereos in the same cars and they all behave perfectly. Only the CLIP+ that acts up in this way.

They probably present some combination of a higher output impedance and/or AC coupled audio. 

It would probably be better to use a ground loop isolator on the audio output and leave the player powered properly.

Already tried using this:

http://www.ebay.co.uk/itm/3-5mm-Earphone-Jack-Ground-Loop-Isolator-Noise-Filter-/280615811526?pt=UK_In_Car_Technology&hash=item41560179c6

Still no audio with two grounds. 

An isolator like that will break DC current flowing through a ground loop (well assuming it works as advertised, who knows on ebay), but will not block AC current.  I suppose its possible you have some low frequency ripple on the ground, which passes through the transformer.  Not sure how that would happen, you'd probably have to get a scope and a good amplifier and take measurements to figure out whats going wrong. 

[TurboZutek]

Double Post! 

[TurboZutek]

Assuming the USB you mention here is still the DC adapter you mentioned above, its because your stereo isn't wired right and voltage between the AUX jack and the car's ground that pushes enough current to trigger the overcurrent protection.

Hmmm, I'll call Volvo, Toyota and Hyundai tomorrow and tell them they don't know how to wire a car stereo. 

Thats not surprising, there would be no ground loop in such a case. 

Yeah, that's what first confirmed the idea it was a ground loop problem to me. I'm still not 100% convinced it's an actual over-current tripping the amp section off though; instead I wonder if it's an oscillation (from ground loop or something else) that's just wiping out the signal as it runs through the amp. I'd have thought that even in a terrible design, over-current in the amp would shut the whole player down.

The purpose of overcurrent protection is to keep you from melting your player by plugging into incorrectly wired stereos.  Since you launched enough current into the device to trigger the protection, and the player wasn't destroyed in the process, I would say its doing quite a lot of good.  Without it you'd might be looking for a new MP3 player and/or car stereo. 

I'm glad that none of the other devices I use are so sensitive to what appears to be a wide spread global problem. Blackberry, Garmin, Nokia, Apple and a host of other cheaper Chinese MP3 manufacturers seem to have managed to design in either compensation or tolerance to this issue, pity SanDisk didn't.

I don't mind a $20 MP3 player and a $15 head unit going pop... $300 smart phone or sat nav?? Not so much!!! 

They probably present some combination of a higher output impedance and/or AC coupled audio. 

For the purposes of Science, we'll call this configuration and design 'better'.

An isolator like that will break DC current flowing through a ground loop (well assuming it works as advertised, who knows on ebay), but will not block AC current.  I suppose its possible you have some low frequency ripple on the ground, which passes through the transformer.  Not sure how that would happen, you'd probably have to get a scope and a good amplifier and take measurements to figure out whats going wrong. 

If so that's weird: I get this problem with the car switched off. No alternator, no cooling fans, nothing on except the stereo itself and possibly the memory wiring for the ECU's. I'd have thought most suspects in an AC fault would have been out of circuit at this time. Even then, the head unit and the USB PSU both have inductors and chokes in the power section that should take care of it, I'd have thought?

/Although I'm not sure the PSU has inductors on the ground, come to think of it.


-----------------

Anyway, in terms of what I can do, could I try the following (just to test, of course):

1. Restore power ground and remove signal ground

2. Rewire signal ground at the head unit to the power ground (That should remove the loop, if there is one, right?) - so I'll leave L and R going into the head unit but take the signal-ground wire and common it with Power-Ground.

As I said before, the MP3 player is worth about $20 and the head unit I'll use for testing (in the Volvo) is sixteen years old and worth about $15 - so I don't mind taking the 'risk' and trying a few things out!

Chris...

PS: I think there's a ground loop in the forum too, I posted a reply to this last night (that I can see in 'topic summary') but it isn't visible on the thread. 

[TurboZutek]

Ok this morning I thought I'd try a combination of 1 and 2 above.

I re-established the POWER Ground on the USB PSU and removing Signal Ground from the 3.5mm connection. Charging works OK and the audio signal is good too! 

So I guess to get this working on an AUX in connection, you'd have to make up a special lead which has no ground. 3.5mm male to 3.5mm male with L+R hooked up but nothing else, would do it. I will try this on the other cars and post back if it works.

I think this layout should mean the charging (high currents) can run nicely out their own ground and the music (very low currents) can use that ground too: eliminating the ground loop. While this way seems sub-optimal (vs just plugging it straight in and it working like with my other stuff) it is probably an easier and safer workaround than before.

Can anyone see a downside to this way around?

Chris...

[nonob]

Hi,

I have the same pb on my two cars.

I think it is more secured to unplug signal ground instead of power ground but i would like to be sure it is a entire safely way ? even at high volume and even with a car power amplifier (even more high volume ).

Thanks

[nonob]

Already tried using this:

http://www.ebay.co.uk/itm/3-5mm-Earphone-Jack-Ground-Loop-Isolator-Noise-Filter-/280615811526?pt=UK_In_Car_Technology&hash=item41560179c6

Still no audio with two grounds.

Many of the ground loop isolators (particularly those sold on eBay) have a current rating on them. Preamp level noise filters (ground loop isolators) essentially have no current passing through them. There is a very tiny bit of current that's required to pass the audio signal but it's less than 0.0005 amps of current in most cases. The old style noise filters that are used in the B+ line must pass current but those are rarely used (and when they are, they're genrally useless). Preamp level ground loop isolators have RCA connectors and rarely have power/ground connections. If you're looking for a ground loop isolator and you see a current rating on them, it's not likely made by a trustworthy company.
source: http://www.bcae1.com/glisoltr.htm

It seems that this model from "PAC" brand fix the problem :
http://pac-audio.com/productDetails.aspx?ProductId=193&CategoryID=31

See last message here:
http://forums.sandisk.com/t5/Sansa-Clip-Sansa-Clip/clip-doesn-t-play-music-when-charging-in-car/m-p/143234#M29009

But i have a question.., i saw on others message that some people have the problem only after a sansa firmware update
(http://forums.sandisk.com/t5/Sansa-Fuze/Charging-while-playing-problem-since-update/td-p/68118/page/2), first i think that because im' using rockbox i can exclude it is a sansa firmware bug ?

But even if i use rockbox, is there a part of sansa firmware which is always used by player.. somewhere... (do you think that reinstall rockbox with a older sansa firmware (.bin file for dual boot) can be a good try ?

cu

[nonob]

Hi,

I did some test yesterday:

1-Unplugg audio ground only:

The sound is back but with noise.I can hear it very well when i do "pause" or when i listen quiet music.
It is not a good way for me.

2-Unplugg power ground:

My sansa clip + rebooted and did a electronic overcurrent sound (not from audio but from player!!!!) , i've been afraid !!

I unplugg all very quickly!

It works again but i had a saturate sound on my speakers !

I tried other source from head unit and it was the same!

I powered off my head unit and rebooted it: It works  

Not a good way for me  


3-I tried power my cigarett lighter to USB adaptator directly from battery:
Same pb: sound muted.

4-I tried all these tests in my another car:
All results are the same (audio noise when audio ground disconnected too...).

In fact,  i don't need to connect power supply for the sound is muted, if only the ground of sansa's microusb connector is connected to a ground anywhere in the car: the sound is mutted!

Anyway, i see only two solutions for me:

-I listen to my music with battery only  
-I buy a "good" ground isolator like the PAC mentioned above, but i hope with it i would not the same audio noise that when i disconnect audio ground..., i don't want to lose money..

cu