Support and General Use > Hardware
using sansa clip+ in car
saratoga:
--- Quote from: TurboZutek on April 01, 2012, 06:24:25 PM ---The signal ground for the Audio will become the ground for the charger and the amplifier in the CLIP+ will stop ground-loop oscillating.
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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.
--- Quote from: TurboZutek on April 01, 2012, 06:24:25 PM ---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.
--- End quote ---
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?
--- Quote from: TurboZutek on April 01, 2012, 06:24:25 PM ---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.
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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:
--- Quote from: saratoga on April 01, 2012, 07:01:10 PM ---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.
--- End quote ---
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.
--- Quote from: saratoga on April 01, 2012, 07:01:10 PM ---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?
--- End quote ---
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! ;D
--- Quote from: TurboZutek on April 01, 2012, 06:24:25 PM ---A ground loop generally happens because the stereo is wired up properly to the car battery.
--- End quote ---
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!
--- Quote from: yapper on April 01, 2012, 07:15:15 PM ---It would probably be better to use a ground loop isolator on the audio output and leave the player powered properly.
--- End 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. :(
It's weird, hey?
Chris...
saratoga:
--- Quote from: saratoga on April 01, 2012, 07:01:10 PM ---Why would there be an over-current when the player is being charged from USB? ???
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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.
--- Quote from: saratoga on April 01, 2012, 07:01:10 PM ---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.
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Thats not surprising, there would be no ground loop in such a case.
--- Quote from: saratoga on April 01, 2012, 07:01:10 PM ---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!
--- End quote ---
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.
--- Quote from: saratoga on April 01, 2012, 07:01:10 PM ---
--- Quote from: TurboZutek on April 01, 2012, 06:24:25 PM ---A ground loop generally happens because the stereo is wired up properly to the car battery.
--- End quote ---
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.
--- End quote ---
A quick look on google suggests that ground loops are extremely common in car stereos, so I guess that is not surprising.
--- Quote from: saratoga on April 01, 2012, 07:01:10 PM ---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.
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They probably present some combination of a higher output impedance and/or AC coupled audio.
--- Quote from: TurboZutek on April 01, 2012, 06:24:25 PM ---
--- Quote from: yapper on April 01, 2012, 07:15:15 PM ---It would probably be better to use a ground loop isolator on the audio output and leave the player powered properly.
--- End 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 ---
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! ;D
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