Soldering BNC connector and Power Supply

I've got a Digi + Pro and Rpi 3B+ and ... an a linear power supply.

My plan was to solder a 75 ohm BNC connector and a connector for my linear power supply. 

The BNC seems straight forward.  The power supply seems quite controversial. 

I started with this guide: https://www.hifiberry.com/docs/hardware/digi-pro-external-power-supply/   Which seems out of date - we no longer need to cut power to the Rpi -  but doesn't go on to explain how to set it up for the new boards.  It does imply v cx that this was something that was done with some regularity.  

Trying to find newer (within the last couple of years) info on this forum turns up responses suggesting that people are wasting their time and going to void the warranty.  

I will void the warranty by adding the BNC connector anyway so I'd like to focus on whether or not I'm wasting my time.  My power supply has a miniUSB adapter so I can plug it into the Rpi directly.  

Are all the folk who suggest quality improvements by supplying power directly to the Digi + pro (and powering the pi through the Digi+ pro) just fooling themselves?  And why is the P3 power header on the Digi+ pro if not for this purpose? 

Finally.  Is the square pin (lower near the P3) the negative? 


Thanks everyone. 


Please sign in to leave a comment.