Hello , it doesn’t make sense to me but I went from 250 gb download -10 upload to 1000 gb download and 40 upload with a new modem and the audio quality is significantly improved. Not kidding.
How can this be ? I don’t understand it . I’m listening to Tidal here.
Depending on your network, the new modem hardware itself may have some impact compared to the old one with regards to electrical noise (though not very likely).
ISP speeds do not have any influence at all – there’s no magic in networking. I’d love it to be the case though – ample room for improvement with my measly 20/3Mbit countryside DSL line. 
I don’t understand it but there must have been some additional noise in my network setup that’s gone now .
Could be a packet priority assigned by your ISP based on the price tier.
Well the difference is not subtle .Pretty happy .