Yes @NickAlexeev, though single-turn screwdriver-accessed trimpots on front. But I'm building a little add-on box - digital meters and fast current limiters.
@W5VO The batteries cant be in series due to space limitations. I want to make the speaker as portable as possible and be able to be charged using a USB cable. So looking to get very long runtime and very loud audio out of it. Portable, small and durable.
A speaker that can fit (not perfectly comfortably) but nice enough to fit in large winter jackets. Something I could use at the beach for 8 hours or much longer at max volume. Or something I could use at the beach and then use immediately once I get back to "base camp" so to speak and continue to listen to music or a movie or something I've downloaded for an additional 8 hours. Something that can be used for a couple days without needing a charge.
So centered around camping and not glamping
I do want my speaker to be able to charge and run the battery at the same time. So any options or information on modules that could work with the voltages and set up I have would be welcomed.