Here’s a demo of the speakers working and when the interference happens.
This should help with understanding the problem I’m trying to solve.
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Thanks James, hopefully the videos I posted above make things clear. 
Hi Jacques
Not exactly the detailed wiring diagram needed. The video shows no detail, just a few wires going to blobs.
Your previous sketch shows the converter input and output reversed. What has been done about that. If this one is reversed it may be a terminology problem and all may have been connected reversed.
If you look at the page linked for the converter you will see a view of the bottom of the board with connections marked. "V0+ is the output (5V) and should go to earbud charger, “GND” should be self explanatory (-veV common), IN+ is converter input (12V) goes to 12V supply and “EN” is enable. Don’t know what you need to do with enable but you should do something. Your documentation that came with the unit (joke???) should tell you.
Cheers Bob
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Hi Bob, sorry for the mistake in my schematic.
I do have 12v going to the IN+ point and V0+ is providing 5v output to the earbud charger.
I have updated the schematic now to make it accurate.
Did you watch my video above demonstrating how and when the interference problem happens?
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Hi Jacques.
Yes I did watch and listen. Will do so again later
I am still puzzled why the single battery appears to be connected to the same point as the earbud output / amplifier input. Possibly this is not the case put it appears to be.
I see what has happened, your picture of the inverter showed top view and your connections should have been for the bottom view. You claimed everything to be correct but this sort of error really confuses the issue. Think of what it would be like if this sort of error happened all the time in the commercial world.
You still have done nothing about the “enable” connection. I think this has to be connected somewhere. If left floating it could be anything and maybe the converter is switching on and off very rapidly creating your interference. Do something about this and see what the result is.
Another thought. These earbuds would not be charging and used at the same time as the charging system seems to be in the storage box. It is quite possible then that this “interference” could be normal with this design and there is nothing you can easily do about it. The only solution then may be to revert to a plug in charging system, charging to be carried out when not in use. Like it would be normally. You have tried 3 converters with the same result so It may be the charging system causing your problem and not the converter. However I suggest you do something about the “enable” connection before anything else.
Cheers Bob
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