Not sure why this isn't working... Works in Chrome fine but Safari won't play it at all.
<audio controls loop>
<source type="audio/wav" src="https://www.dropbox.com/s/33wzzsmpe6a94l4/amitabha%20mantra%20from%20tbco.wav?dl=1" />
</audio>
See if Dropbox has a direct, non-redirection URL to use. The URL you provided returns a 302 redirection URL:
$ curl -I "https://www.dropbox.com/s/33wzzsmpe6a94l4/amitabha%20mantra%20from%20tbco.wav?dl=1"
HTTP/2 302
location: /scl/fi/xoigkdohbn98m8le03e2d/amitabha%20mantra%20from%20tbco.wav?rlkey=2jrpdkg90bxmqo2ijczc3uqbd&dl=1