The Tunedock is the best amplifier for your phone that doesn't require electricity. No wires, no pairing, just play your music on your phone and place it in the dock. Simple, right?
Various different CAD formats (available at https://a360.co/2MgwsxX)
Recommended print settings
Full size, 10% infill, 0.4mm nozzle, 0.2mm layer height, 60mm/s speed, 2 shells, No supports, Skirt
Buy a Tunedock
Buy for $180 (Sorry about the price. Almost none of this money is going to me.)