Transcode to 192 : the sound is broken up

[simoncn]

I tried this on my DS211 which has a similar processor to your DS413j.

I saw CPU jump to 100% near the start of the track and drop to below 20% after that. Playback was smooth with no audible issues.

When I am not playing music, CPU is very low (between 0% and 10%).

Is your CPU low like this when not playing music or is it higher? If it is higher (you said it is "always" 100%), it is probably a CPU overload issue. If CPU is low when music is not playing, it is more likely to be a network issue. This could be caused by a bad (or old and slow) network cable, so try changing each of your cables to see if there is any difference. A bad network cable that is forcing a lot of retransmissions of corrupt data could increase CPU load.