I have a Bluetooth subwoofer that came with a sound bar, I have replaced it with a wired one, and would like to use this one with my digital piano, but there is no analog input on the side. Would it be possible to add one so I could supply an input without Bluetooth?
Maybe, maybe not.
It’s entirely possible that its signal path is all digital. You’d have to dig around on the inside to find out. Look for recognizable op-amp part numbers.
It’s a 180-degree tack from where you’re looking, but would this, or something like it, be a feasible solution?
https://www.amazon.com/Avantree-Bluetooth-Transmitter-Receiver-Headphones/dp/B00LAZ6RTW