USB External DAC maximizes one CPU core while playing

Hello all!
Nice to be part of the community! I've installed Ubuntu Mate 19.04 and, while using youtube or VLC on my laptop through my Chord Mojo USB dac, I have high CPU temperature and Fan going on. By a closer look seems that the CPU7 of my i7700HQ goes to 100% while other threads/cores are not invovled in the effort.
What could this be due to? This has been happening since I got the DAC some months ago.

Thanks and cheers to all
D.