I'm going to try and build my own battery pack for a portable speaker. It uses 20 volts and 3 ampere as input. I realize I will burn through quite a few batteries if trying to power it with just AA or even D type batteries. That's not a problem, the problem is that I'm a bit rusty when it comes to my electrical knowledge.
What I would like to know is if I need some kind of regulator for something like this, or if it's enough just to keep below the 20 volts and the device will automatically draw the right amount of amperes? This would mean that I could connect thirteen 1.5 volt batteries in serial to get roughly 19.5 volts out. Or do I also need to parallel connect those 13 to get the right amperes?
So, for you TL;DR people out there:
How would I connect AA or D batteries (serial/parallel) to power my 20V/3A device? Do I need some regulator type device for it, or is it safe if kept below those values? If I need some regulator/other for my desired setup, what can you recommend that's suitable for my situation?