Thank you for putting me right there. I was EXACTLY wrong; it's a minimum of 1A, preferably a good 2.1A modern charger.

I've found Belkin and especially Aukey recommendable.

Ask anyone over 40. They'll have a drawer full of weak chargers and will give you one. They can't do any harm if 5V micro USB.

Try an older phone charger with a low enough output maximum to force a cooler trickle charge; maybe a 750mA or or even 500mA. Could be wrong but I think despite modern 5V chargers being 2.1A the Mojo only takes 1A max.

Most likely your headphones clipping, but interestingly, above a certain volume (it varies depending on individuals) the tiny bones that transmit sound in your ears create their own distortion. (tldr: your ears can clip)

Lithium batteries survive best when cool and at about 65% charged. They deteriorate more rapidly when hot and either fully charged or flat.

Yes, what would you like to know?

Just a note in praise of the Mojo, this is major: Sold off my vinyl deck many years ago (Source, Zeta, Koetsu) and despite High end amps and speakers not been satisfied since then. Been (wrongly) waiting for an upgrade in digital source DVDA SACD etc but it proved the answer that eluded for so...