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For further information and assistance, we highly recommend visiting our Sony Global Web site for information on contacting the Sony Support Center in your region at http://www.sony.net/SonyInfo/Support/.
Greetings and thank you for your message, we apologize for the delay on our response. If you still want to be able to use an external charger you can use the USB CA power adapter model AC-UD10, also we cannot guarantee that the portable charger will be able to charge the headphones, if you are planning to test a portable charger make sure that it outputs a DC 5.0 V with a rated output current of 1500 mA.
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