Weird crackle with MIDI clock out

I don't know is it MPC or my soft, but I get lo-mid freq crackle (pretty dense and low volume) when sending clock out to software synth, NI Reaktor 4. It's most noticable when it changes to desired tempo, but even when it's set I still hear it. It only goes away if I turn clock to OFF on MPC..
anyone slaving soft to MPC to check? it's on os2xl

you hear it from the mpc audio out or the software?

probably some crosstalk... i notice it with the mpc 1000. not the cleanest.

It was from software. I think I got it solved, it's some driver issue.. because I fired up same setup this morning and everything was clean.. I thought wtf. So I opened Chrome for a while, put some music for 5 sec, closed. Opened soft... BAM crackle..LOL
I forgot it's best to use soft on a restarted PC..