Mmmm... on further listening I started to notice audible clicks and artefacts. I was using, what I think, is a USB C to USB C charging cable only.
Sound I realised after a bit of listening was a little rough, I think the iPod classic sounds much better.
Further research suggests an OTG cable is required, so have ordered a couple to try.
Within this research I find out that Android upsamples the audio it outputs to a DAC, aha that explains why Spotify was showing as 96kHz on the Mojo.
Some suggestion OTG works around this, some suggestion it doesn't and a couple of music player apps might do the job... oh no, third party apps and no I'm not going to get into rooting the device.
Ah, this is why I wanted to avoid smart phone to DAC/headphone amp. Nightmare and so far not happy with the sound at all.
Will try the other cables when they arrive, but I suspect the Mojo might be going back for a refund.
Anyone know if Android based DAP's avoid the Android drivers upsampling audio before it hits their internal DAC's... ?