I use pacpl. It works for so many formats you may find yourself feeling as though you're in a candy store.
It hasn't failed me yet(knock on wood)

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audiokonverter is rich in content choices but often makes ugly sounding files for me.
pacpl is is the only converter I have found that accurately converts to an mp4 that works on the shuffle.
I haven't tried flacon but I will now.

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good luck.