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Soldering BNC connector and Power Supply

Jim Meyer

October 21, 2020 16:42

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I started with this guide: https://www.hifiberry.com/docs/hardware/digi-pro-external-power-supply/   Which seems out of date - we no longer need to cut power to the Rpi -  but doesn't go on to explain how to set it up for the new boards.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

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5 comments

• 0
  
  David C. Snyder October 28, 2020 17:42

  Following. I'd be surprised if separately powering the Digi+ Pro makes a meaningful difference, but I suppose it depends on the characteristics of the downstream DAC. Which DAC are you using?

• 1
  
  Jim Meyer October 28, 2020 17:51

  I have a Hegel h390 integrated. DAC and Streamer. Overall I love it but It's Roon support is vaporware and I wanted to try Roon. 

  BNC connection is nice and clean. The only downside is that the Hegel won't wake up from a signal over BNC. Only from a signal  over it's own network input - which I've grown to love. Using Airplay or a UPnP control point I can just hit play and things come to life. 

  For the time being I went ahead and powered the both boards through the Rpi 3B + using the external power supply.  I am happy with it but still wondering if there is something to be gained by powering both boards through the Digi+ Pro.  Or what the downside is. 

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  David C. Snyder October 28, 2020 18:09

  The h390 is a fairly modern system, so I imagine that jitter/noise rejection from the S/PDIF input is quite good. Besides having to use two power supplies, I don't think there's any downside, but there's probably no benefit either.  :)

  The h390 has a USB input as well. Can you wake it up by sending it a signal over USB?

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  Jim Meyer October 28, 2020 21:23

  USB doesn't appear as an output option on my computer unless the Hegel is already awake. Also, when I select the USB as an output from my macbook the awake Hegel won't automatically switch to the USB input.  It will stay wherever it was most recently.  Only network or Airplay seem to have this ability to wake it up and change its input.  So I doubt it would have a different behavior or additional wake up behavior on another device. 
  
  But because you mention it... Does the Digi+ send a signal out of USB ports on the Rpi board?  Is this an additional output?

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  David C. Snyder October 28, 2020 22:06

  If you connect a USB cable to the h390, Roon should see it as a 2nd output that you can enable in Audio Settings. You could group the S/PDIF and USB connections into the same zone in Roon to compare, etc.