Hey andy...I tested hifimediy sabre usb dac,the sound is good but not extraordinary,the difference between the volume levels it's less than before.(my car have a stock JBL audio system with 8 sp+amp+sub,sound quality in very very good on the radio or cd,maybe that's why the sound is not amazing)
What I can do to stop the screen entering in sleep mode,from the settings can't disable this mode(i have to choose between 15 sec and 50 min).I must install Tasker to do this job?
Belkin sceen protection is ok?
There's an option under Developer Settings (which is probably still hidden on your device) that allows you to keep the screen on when charging. If that option is activated, the timer will only dim the screen rather than turning it off.
Search for Developer Settings at the bottom of the Settings page. You can find it near to "USB Host" option. If it's not present scroll down to the last option "About Phone", look for "build number" and tap on it 7 times. After that you should see a msg saying that Developer Settings is enabled and you should be able to see it on the list.
As for the Sabre... well... it sure did the trick for me, but of course the audio system is fundamental to the end result and should vary. But it's definitely an improvement to the internal DAC/jack connection.