any idea how long those on 9V last before you need to change the batery?

Well yea want DIY and it doesnt have to be powered by powerbank, just i want it to be something rechargeable and with enough capacity to last over 10 hours, also i forgot to say i need it to be portable. Plus i live in EU so shipping from US might be a problem

Hello, as title says iam looking for headphone amp powered by powerbank all i nneed is diagram with description on each component (iam NOT eletrical expert), i tried look on this forum and on google but all i found are just powered by 9v bateries and iam trying to find this diagram powered by...