@TRA: is your HTC One M7 rooted and is a powered USB hub needed between OTG cable and DAC? I didn't realise the M7 is cabable of digital audio output, currently use Bluetooth-aptx to throw a digital signal to the DAC
Nope, not rooted, running 4.4.3 - although I have enabled developer mode. No hub needed.
I bought a little OTG cable from amazon, think it was £5 or something. Literally just Phone > OTG cable > USB to Fiio
Works well.
@TRA: is your HTC One M7 rooted and is a powered USB hub needed between OTG cable and DAC? I didn't realise the M7 is cabable of digital audio output, currently use Bluetooth-aptx to throw a digital signal to the DAC