# USB power to tablet...noise w/ 12V->5V converter



## charliekwin (Apr 22, 2012)

So I recently resurrected my Nexus 7 install after dropping $40 on Timur's Kernel (sigh), got everything hooked up and found out that the buck converter I got is introducing some really nasty noise in my system.

I'm using a cheap unit I picked up on eBay ( DC DC Converter Module 12V to 5V 3A 15W Duble USB Output Power Adapter | eBay ). Am I correct in assuming that that's what's causing the problem?

Would a different converter like this one get rid of the noise? DC to DC Buck Converter High Power Step Down Car Power Supply Voltage Regulator | eBay

Better options/fixes I should know about?


----------



## Victor_inox (Apr 27, 2012)

power supplies can be awfully noisy. If you don`t mind making your own here is a good readInvalid Request


----------



## charliekwin (Apr 22, 2012)

Electronics like this are one area where I'm a little out of my depth and the schematic there looks like it's on the edge (okay, probably a bit outside) of my comfort zone.

Having inadvertently spent way too much money (and time) on this stupid project, it sucks having this bring it to a halt. Am I likely to have any luck with one of the step down converters on Amazon or eBay, or is this an installation or environment problem that a new converter isn't going to solve?


----------



## Victor_inox (Apr 27, 2012)

charliekwin said:


> Electronics like this are one area where I'm a little out of my depth and the schematic there looks like it's on the edge (okay, probably a bit outside) of my comfort zone.
> 
> Having inadvertently spent way too much money (and time) on this stupid project, it sucks having this bring it to a halt. Am I likely to have any luck with one of the step down converters on Amazon or eBay, or is this an installation or environment problem that a new converter isn't going to solve?


this one should do it:12A 100W Adjustable DC Step Down Convert Battery Buck 5V 12V Car Power Supply L | eBay


----------



## SPLEclipse (Aug 17, 2012)

Why did you pay for Timur's kernel? 

I use this adapter in my nexus install. It's branched to go to the OTG cable from the 2A outlet and a non-powered 4 port hub on the 1A outlet. The hub has has a 320gb WD HD and a DAC on it. I always have a 100% charge and no noise, even if i switch from the DAC to the headphone-out on the tablet (well, it's a little noisier with the internal DAC, but just barely).

Dual-Port USB Car Charger Adapter for Apple iPhone iPad iPod | 125-362

Here's the hub I'm using in case you need one as well.

Belkin 4-Port Compact USB Travel Hub Silver | 139-056


----------



## charliekwin (Apr 22, 2012)

Appreciate the suggestions you guys...I'll order and hope one works out. At least they're cheap.




SPLEclipse said:


> Why did you pay for Timur's kernel?


He decided not to release the 2013 kernel for free. Disappointing, but I tried a number of kernel and ROM combinations and none of them worked, so I didn't have much of a choice :-/


----------



## SPLEclipse (Aug 17, 2012)

Ahh..I didn't know he was charging for the 2013. I know he originally rejected the idea of doing it and then came around, but that was the last I heard. $40 is really steep though.

Good luck man!


----------



## Burksdb (Apr 28, 2011)

i run a nexus 7 in my car i know with a thin cable i get noise but with a thicker better quality cable 0 noise and everything works great. I just decided to use a 2.3 amp charger.


----------



## Nismo (Jan 10, 2010)

The noise is likely a ground fault. I had that issue with mine, when using a Griffin adapter, but when I changed to a Belkin, the noise went away.

I'm using a DCDC-USB from mini-box, as soon as I can get it put in.

Eric


----------



## Victor_inox (Apr 27, 2012)

I agree with nismo, it`s almost always ground fault.


----------



## charliekwin (Apr 22, 2012)

I figured as much, since I had the characteristic alternator whine. I found an old cigarette lighter adapter in my Random Box of Crap last and tried that, with no real improvement. BUT, when I physically pushed on the RCA jack in the console, that got rid of most of the noise, so I've got a lead to start with.


----------



## naiku (May 28, 2008)

charliekwin said:


> He decided not to release the 2013 kernel for free. Disappointing, but I tried a number of kernel and ROM combinations and none of them worked, so I didn't have much of a choice :-/


That sucks! I use the free 2012 version, although I donated some money to Timur since it works well. 

Look into a DCDC-USB, its not exactly cheap (around $60) but has been powering my Nexus for about a year now without a hint of noise, and charges the tablet very quickly along with also powering my USB hub.

I also have a cheap eBay converter laying around somewhere if you want it, even just for testing purposes (and assuming I can find it) just let me know and you are welcome to it.


----------



## charliekwin (Apr 22, 2012)

Thanks, I appreciate the generous offer naiku, but I've already got another converter on the way from China that I'm hoping will work. If not, I'll probably have to suck it up and just pay for the DCDC-USB, since other people have reported similar successes with it.


----------



## naiku (May 28, 2008)

charliekwin said:


> Thanks, I appreciate the generous offer naiku, but I've already got another converter on the way from China that I'm hoping will work. If not, I'll probably have to suck it up and just pay for the DCDC-USB, since other people have reported similar successes with it.


No problem, hopefully the one you have on the way does the trick. For me the cheap one I had just barely charged (talking 1-2% on a 90 minute drive) and if I started running too much on the Nexus then it would just drain. 

I was reluctant to get a DCDC-USB, but am glad that I did. I tweaked my output using the software that comes with it to 5.4v and get about 14% per hour charge rate now.


----------



## Nismo (Jan 10, 2010)

My DCDC seemed to make all the difference in the world! It runs sooo much better now.

Eric


----------



## charliekwin (Apr 22, 2012)

The latest eBay converter was better, but still unusable, so I went and ordered the DCDC-USB. Pricey, but if it's as good as everyone says, it'll be worth it. Should be here in a couple days.


----------



## anticommander (Jun 23, 2014)

charliekwin said:


> The latest eBay converter was better, but still unusable, so I went and ordered the DCDC-USB. Pricey, but if it's as good as everyone says, it'll be worth it. Should be here in a couple days.


Did you by chance find a solution? I'm experiencing the same issues with my 2013 Nexus 7.


----------



## charliekwin (Apr 22, 2012)

anticommander said:


> Did you by chance find a solution? I'm experiencing the same issues with my 2013 Nexus 7.


Yeah, the DCDC-USB is working well for me. Not cheap, but sometimes you just gotta suck it up.


----------



## anticommander (Jun 23, 2014)

charliekwin said:


> Yeah, the DCDC-USB is working well for me. Not cheap, but sometimes you just gotta suck it up.


Did you by chance try re-grounding your 12V plug or the RCA cables (if you used any)?

I've done absolutely everything I can think of to no avail.


----------



## charliekwin (Apr 22, 2012)

anticommander said:


> Did you by chance try re-grounding your 12V plug or the RCA cables (if you used any)?
> 
> I've done absolutely everything I can think of to no avail.


I'm not well-versed on electronics, so I may be off base here, but I think I had two problems: dirty power, and a ground loop. Switching to the DCDC helped with the first problem, but I still had a whine. I added an extra ground from the power supply to the head unit case, which took care of the ground loop. Tried adding grounds to the RCAs as well, but didn't notice any difference.


----------



## anticommander (Jun 23, 2014)

charliekwin said:


> I'm not well-versed on electronics, so I may be off base here, but I think I had two problems: dirty power, and a ground loop. Switching to the DCDC helped with the first problem, but I still had a whine. I added an extra ground from the power supply to the head unit case, which took care of the ground loop. Tried adding grounds to the RCAs as well, but didn't notice any difference.


Could you by chance provide me with a link to the product you bought? Thanks for your help!


----------



## charliekwin (Apr 22, 2012)

Amazon.com: DCDC-USB, Intelligent DC-DC converter with USB interface; Convert any Voltage (6-34VDC) into ANY Voltage (5-24VDC) from your Computer under USB control. High current, up to 10A; Driver and example programs available: Electronics


----------

