CS8420 SPDIF grounding question - diyAudio
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Old 21st April 2010, 10:53 AM   #1
diyAudio Member
Join Date: Oct 2009
Location: Brunei
Default CS8420 SPDIF grounding question

Hi all,
I am about to improve the SPDIF input on my Berhringer SRC2496 by connecting a new RCA directly to the CS8420.

I'm just a bit puzzled on the grounding. The CS8420 datasheet shows different ground points for the RCA and the chip, and I could imagine a ground loop if I would connect the ground pin of the chip (pin 5) to the cold of the RCA (RCA is grounded to the star point). On the other hand, what other ground point should I connect pin 5 to?

Or should I just leave it on the board as it should be grounded correctly in original state (in other words just connect pin 4 to the hot of the RCA and that's it?)

Thanks for helping me out here...
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Old 21st April 2010, 11:42 AM   #2
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Join Date: Jan 2008
Location: Virginia
What ground loop are you imagining?
The ground ring of the RCA shall be connected to the board, on the ground, closest to the point where the middle is connected.
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Old 21st April 2010, 12:20 PM   #3
diyAudio Member
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Location: Brunei
Ground loop:

Star point - PCB - CS8420 - RCA ring - Star point
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Old 21st April 2010, 03:43 PM   #4
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So, where does the RCA ground go to? Star point?

And where does the RXN ground go to? Leave it as is as it already should be grounded properly on the PCB? Scratch the laquer off the PCB and ground it to the ground plane? Or ground it at the RCA (via cap)?
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Old 21st April 2010, 03:47 PM   #5
bocka is offline bocka  Germany
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Location: Hannover
Originally Posted by studiostevus View Post
So, where does the RCA ground go to? Star point?
Star ground with RF? This will never work. You need a well defined 75ohms transmission line from your RCA connector to the SPDIF receiver. Use a solid ground plane.
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Old 22nd April 2010, 11:55 AM   #6
marce is offline marce  United Kingdom
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Location: Blackburn, Lancs
Digital should always have a GND plane, star grounds are no good (understatement) with digital. If nothing else the signal is closely coupled to the ground as at these speeds the return path follows the path of least inductance, i.e. dircectly under the signal track, no ground plane means the return has to meander all over = noise, EMC problems etc
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Old 28th November 2013, 04:27 PM   #7
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how to conect xlr aes/ebu spdif to cs8420, can anybody help me? Mayby pictore or something.
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