Couldn't Initialise sound, Not enough USB controller resources

Purchased the FiiO E10K amp/dac, works excellently with everything else on my pc, super pleased. When it comes to playing Apex however a few issues arise.

Some sounds within the game become distorted and crackly, for example mirages in game voice when team mates are pinging items.

Now the game launches and shows this error message;

Engine Error

Couldn't initialize sound.

Please make sure you have a sound playback device that is enabled and properly configured.

Failed In:MilesDriverCreate

Miles output follows:

Audio Hardware Error: Failed to initialize IAudioClient (shared, event mode, float, chans=2, rate=96000, HR=80070001)

Failed to initialized WASAPI audio hardware, trying XAudio,

Couldn't create XAudio2 master voice.

Windows also shows an error message: Not Enough USB controller resources.

Why does this only happen with apex legends, and how can I go about fixing this issue.

Thanks

James