I have a project with about 20 audio tracks. Most of these have EQ on them. They route to buses with further effects such as echo and reverb. Half a dozen of them have automation envelopes on them, for volume or effects levels. Running X3 on Windows 7 64-bit. I've built much more complicated music on this same setup before many times.
 
After leaving this project for about six months, I have just re-opened it and now it crackles a lot. Bypassing effects globally causes all crackling to stop, so something in the effects or automation is causing the crackling. The CPU meters sit around 30-70% when FX is on, about 5-25% when bypassed.
 
To determine the CPU hog, I saved the project to a new name and started removing automation, then effects. One by one as I deleted an effect or automation envelope, the crackles gradually became less and less, and finally when all effects and automation were gone, the crackling was gone. 
 
But with all automation deleted and only 4-5 tracks with EQ still on them, I was still experiencing some crackling. Why? That's hardly anything. Last year I built a whole album with songs with tons or tracks and effects, never experienced this problem. I bought an SSD for Christmas and put everything on it but no difference.
 
My hardware is all the same, (except for the SSD, and I was having the same issue before I installed that). My synths, both soft and rack, are also the same. Everything's the same, except it's six months later.
 
Before someone says "corrupt project" let me also add that I made another song around the same time, and I'm experiencing new crackling with that one too. I haven't gone through all the investigative steps, but just in case someone claims it's unique to this project, it isn't.
 
Any ideas?

Hmm....what video card are you using?...ati? or nvidia?...and mouse?...some mice and video cards have issues with Daws....I find in some windows in certain daws, when I put my mouse over the tracks window or plugin windows...I get clicks and pops...so I do not move my rodent when recording...Yes it is a gaming Mouse logitec G500...But I really like the weight of it when fully loaded with weight...and I feel very comfortable using it....even though I was told to change it to something more simple.
 
HDMI AUDIO on video cards...may be a problem also...might want to defeat that if you are not using it...
 
and if you are not using onboard audio device...turn that off if you can...and nic cards...just to free up some IRQs and see what happens then with a test run..
 Might as well turn off all redundant devices in device manager, like wi fi also...and shut down any third party background apps or virus checker...malware progs...if running em.
 
 
Best of luck....let us know what occurs.
 
 

The thing of it is, whatever I'm using video/audio/accessory-wise is the same thing I was using six months ago. I don't use this computer for much else beyond Sonar projects. No NIC card, no gaming anything, relatively simple mouse. HDMI is used for one of my two monitors, but again, same setup as before.

Did you update the video driver recently or make updates to the OS?
If you feel that nothing has changed....then what causes this to arise?...if it was not before, something has changed Right?....If you do not use the HD audio on the video card..or do not need to...try and see...no harm will come...and if not you can turn it back on.....troubleshooting ...gotta start somewhere.....wink.

any odd weather causing power brown outs or failures of electrical?....parts do ware out...
 
What about defrag?...any word on to do or not to do?....or was it done before moving the data to the new ssd?...

Oh x3?...x3e solved a problem with pro channel noise...but not sure it cannot come back...just thinking out loud.....sorry I see you got that in the descript of your system....but it says x3 in the top part. 
 

You say you are having "crackling," and the assumption is apparently that this is due to an overload of the processor. Assuming that the crackling is due to dropouts, it does not automatically follow that the problem is the result of processor overload. Anything that interrupts the flow of audio data can produce that symptom. For example, too small a buffer, or a look ahead buffer somewhere in the system can interrupt the flow even when you have plenty of computing power. What is the CPU meter showing in Sonar and in Windows when the crackling is there?
 
 
http://windows.microsoft.com/en-us/windows/view-cpu-utilization-performance-information#1TC=windows-7
 

and what are the buffer settings being used....?

M audio Delta not finding that completely as stated...but other models with more numbers at the end...like 10/10...etc/legacy cards and breakout boxes....could be something with the PCI buss?....check shared Irqs in the start /accessories/system tools /system info....and select irqs, and see what is sharing.....?
 

PCI buss...Asus what board?....what chipset?...