i was having issues with long tracks typically over 5 minutes causing crackle sounds while playing Audirvana. I was also having these issues on Youtube while Audirvana was open and not engaged. It did not matter if the file was streamed locally or internet. I posed the question on the Audirvana forum and was recommended to change the file buffer setting in Aud+ Preferences to about 20% of full buffer. That got rid of the noise.
MacBook Pro> USB to SMSL DAC > XLR out to powered Monitors
MacBook Pro> USB to SMSL DAC > XLR out to powered Monitors