Remember you're still at risk of killing it if you don't know the
polarity of the DC socket.
For the record, don't use a 6V plugpack for a 5V device. Also if
you're playing games with plugpacks, remeber the difference between
regulated and unregulated plugpacks. Your bluetooth speaker probably
expects to be used with a regulated plugpack, and an unregulated one
(such as most transformer plugpacks) wouldn't be suitable.
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