Originally posted by neildavis
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Sure enough, the switching frequency between the boards is not sync'd and the magnetics are coupling, showing up as a high frequency whine. Fortunately, the revision of TDA7492 boards I have (rev 3.1) has a test point pulled out for the SYNC pin, and the rework was straightforward and relatively easy. Better yet - it fixed the issue ;).
I'm not sure if the TPA3116 boards will need to be sync'd or not - their magnetics layout is different. I'll have to check that later.
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