Windows Tablet with 5V charging via powerbank to eliminate USB noise

[burdie]

I have been suffered from noise generated (ground loop) from windows tablet charger (12V smps charger) to USB DAC. By modified the charger to 2 prong (with no connection to earth) help to reduce the noise but there are some remaining noise which cannot be eliminated. However, it will be dead silent if powered from built-in battery. Do the same test on another notebook (19v charger) also giving the same type of problem.
 
Instead of getting Schiit Wyrd, iFi iPurifer or other USB isolator, transformer isolation or custom linear poser supply (12v or 19v) which may be costly in order to fully eliminate noise, I am looking into other option, new windows tablet with 5V charging, which may be cost cheaper. (Some people may question me that I can get away with the noise by running solely on built-in battery, but the waiting time to get the device fully charged is killing)
 
Toshiba, Acer, Lenovo and many others have introduced 7-8" windows tablet that runs on Windows 8.1 with Bing, and the price is dirt cheap, some go for USD $99 only. The common specs are Intel Atom quad core, 16/32gb emmc/ssd, micro usb 2.0 port and microsd reader, wifi/bluetooth, 1gb/2gb ram etc and 5V usb charging
 
I need anyone that already own these new and small tablets to confirm the following things
 
1) since most USB charger also using switching mode power supply, playing audio while charging may generate noise to DAC.
2) using powerbank or 5v linear psu to charge the tablet while doing some audio playback, very unlikely will generate noise to DAC
3) 1gb ram sufficient or not to run foobar2k/Jriver and decode DSD/DXD hi-rez audio file in asio native mode / down sampling mode 
 
How to test? connect the charger, play any audio file in your tablet using foobar2k or others, pause the playback and don't close the program, turn the volume knob of your headphone amp/speaker amp/ DAC with headphone by more than 50%, and listen for any possible humming/noise come out from your headphone/speaker.

 

[AlrightMister]

Hav you looked for a 12v linear power supply? Should be pretty cheap. Is the battery life on your tablet bad or do you listen for long periods? I have a Dell venue 8 pro and a usb Schiit Modi but I dont have a usb otg split charging cable. Can't charge and connect to my DAC at the same time. Not sure the power bank will work. They are usually a single cell stepped up to 5v or 2 cells stepped down, switching or they would be hot and inefficient. I doubt you'll find a linear one. 

 

[burdie]

  Hav you looked for a 12v linear power supply? Should be pretty cheap. Is the battery life on your tablet bad or do you listen for long periods? I have a Dell venue 8 pro and a usb Schiit Modi but I dont have a usb otg split charging cable. Can't charge and connect to my DAC at the same time. Not sure the power bank will work. They are usually a single cell stepped up to 5v or 2 cells stepped down, switching or they would be hot and inefficient. I doubt you'll find a linear one. 

Standard DC jack for custom linear power supply is using 5.5mm*2.5mm. My tablet used DC jack of 2.5mm*0.7mm. Need to 100% sure that no more noise before commit to buy.Furthermore, custom linear power supply is much more expensive than those small windows tablet. Cheapest with knows quality linear power supply already cost almost double to the cheapest windows tablet available.
 
My Samsung Ativ smart pc pro's battery only last for about 2-3 hours (reduced life spam of the battery?) after fully charged. Sometime I forgot to charge the battery so on next use I have to plug in the charger then cannot stand with the noise. This tablet is using core i5 with bigger screen size so no way it can have long battery life. Windows tablet with smaller screen size and power-saver atom cpu will definitely give longer battery life than power hunger core i5.
 
I didn't know that Dell Venue 8 pro only have one usb port for both data transfer and charging as I saw some tablet with another charging port. Will usb otg cable with usb hub able to do data transfer (DAC and external HDD) and charging simultaneously? 

 

[AlrightMister]

Why do you need a custom power supply? Find a cheap 12v linear wall wart and solder on the needed barrel connector for your tablet. If you're looking at audiophile grade power supplies for your tablet you are better off buying a usb decrapifier. Cheaper and can be reused for any future usb DAC.
 
The 8" Windows tablets are all going to come with switching power supplies too so if you go that route you will still likely need to source a 5v linear power supply and split OTG charging cable. You could then still end up with some noise as cheap linear pwr supplies are unregulated and probably have little filtering. I think the best solution, to spend some money one time and not keep chasing the issue is to spend $100 on a Schiit Wyrd.

 

[burdie]

  Why do you need a custom power supply? Find a cheap 12v linear wall wart and solder on the needed barrel connector for your tablet. If you're looking at audiophile grade power supplies for your tablet you are better off buying a usb decrapifier. Cheaper and can be reused for any future usb DAC.
 
The 8" Windows tablets are all going to come with switching power supplies too so if you go that route you will still likely need to source a 5v linear power supply and split OTG charging cable. You could then still end up with some noise as cheap linear pwr supplies are unregulated and probably have little filtering. I think the best solution, to spend some money one time and not keep chasing the issue is to spend $100 on a Schiit Wyrd.

Thanks for your advice. Sadly I cannot find any 12v linear wall charger, those available are all SMPS as linear psu are just too bulky.
So Schiit Wyrd able to eliminate ground loop?