Because said boxes are not a sure thing to support USB sound cards, the only way is to plunk down your 6 or 7 dollars and try.
Example: https://www.amazon.com/Best-Sellers-Electronics-External-Sound-Cards/zgbs/electronics/3015427011
As to RCA, you only need the usual headphone to RCA cable.
I need to know if it is possible to connect a wireless headset the uses RCA Jacks to an Android box using a USB adapter set of RCA Jacks?

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