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[Advice Needed] DAC Balanced output filters + Gain stage
[Advice Needed] DAC Balanced output filters + Gain stage
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Old 1st December 2020, 04:56 PM   #1
Hofmann is offline Hofmann  Netherlands
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Join Date: Apr 2018
Default [Advice Needed] DAC Balanced output filters + Gain stage

I want to add balanced xlr outputs to my DIY CS4398 DAC.
I am honestly a little clueless in my design choices, so any advice would be appreciated.

Mainly: Is this the right way of doing balanced volume control using opamps?

Secondary: I plan on adding a relay to pull the signal to ground to mute (see the flags labeled 'mute' near the volume control pot). However with this method will leave the signal trace on the pcb open when not muting and I'm worried it will work as a nice little antenna for EMI.

The output filter stage is taken directly form the CS4398 datasheet.

I've also added a screenshot of my current progress with the pcb layout. Something got messed up with the component annotations, so these might not correspond with the ones in the schematics.
Attached Images
File Type: png output filter.PNG (33.1 KB, 60 views)
File Type: png Volume and Buffer Stage.PNG (35.1 KB, 64 views)
File Type: png image_2020-12-01_175359.png (300.6 KB, 59 views)
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Old 1st December 2020, 06:01 PM   #2
rayma is offline rayma  United States
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Join Date: Apr 2011
The muting could be a short between the phases, rather than connecting each phase to ground.
The volume circuit should work ok.

Last edited by rayma; 1st December 2020 at 06:05 PM.
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Old 2nd December 2020, 01:09 PM   #3
Hofmann is offline Hofmann  Netherlands
diyAudio Member
 
Join Date: Apr 2018
You are right, I was plan on doing it this way but I guess I forgot that while typing the post.

However when the signal is not muted, the open traces to the relay might pick up interference. Is this a genuine concern or am I just overthinking it now?
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