crackling sound, random when playback. and also in rendring.

Check you sample rate.  You may want to also check the buffers of your audio device. They could be either too high or to low. 
 
 

Thanks for fast reply.

I think you got your answer, but I find that I need to go to Preferences | Drivers | ASIO Panel and set my rate LOW (like 256) when tracking to avoid latency.  Then to use Melodyne and to mix, I open it back up and set it to 1024.  I forgot one time to turn it back up and was horrified by the crackling and noise.
 
Note that the scale in that panel has simple digits (like 4, 5, 6) but when you slide to a number, you can see the real number (like 512, 1024) change.  I believe 6 is marked as the default and it usually sounds OK but the lag (latency) when recording is annoying--on my system at least.