Support and General Use > Hardware
using sansa clip+ in car
TurboZutek:
--- Quote from: saratoga on April 01, 2012, 08:03:36 PM ---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.
--- End quote ---
Hmmm, I'll call Volvo, Toyota and Hyundai tomorrow and tell them they don't know how to wire a car stereo. ;D
--- Quote from: saratoga on April 01, 2012, 08:03:36 PM ---Thats not surprising, there would be no ground loop in such a case.
--- End quote ---
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.
--- Quote from: saratoga on April 01, 2012, 08:03:36 PM ---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.
--- End quote ---
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!!! :o
--- Quote from: saratoga on April 01, 2012, 08:03:36 PM ---They probably present some combination of a higher output impedance and/or AC coupled audio.
--- End quote ---
For the purposes of Science, we'll call this configuration and design 'better'.
--- Quote from: saratoga on April 01, 2012, 08:03:36 PM ---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.
--- End quote ---
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! :D
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:
--- Quote ---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.
--- End quote ---
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 :P
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
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