greg54
 
When I play the song back, the only thing that's distorted is the guitar track - not the whole track; just certain things, like the lower notes, or if I play high notes a little too hard (even though the signal is not hot at all).

 
It might help to use a volume envelope on the guitar track, turning the volume down on the parts where it distorts, and turning it back up after you play the notes that distort. Record the track, add the volume envelope, turn it down at the places where the audio distorts, and then delete the audio or mute that clip, but keep the envelope. Record the track again with the envelope in place. If it still sounds distorted lower the envelope nods in those certain places where it distorts. Then try recording the track again until you get it where it doesn't distort in those certain places.
 
Hope that makes sense. Or you will just have to play with discipline so that you don't play so loud at those certain places to avoid distortion.
 
Hope that helps.

OH yeah, have you tried connecting your guitar amp straight into the audio interface input with Hi Z on? Use your audio interface's Auto Sens feature to adjust the input signal level. If it goes well that way, you may need another appropriate mic to record the amp or you will have to try a virtual amp plug in that you find suitable, and connect your guitar directly into the input on your audio interface.
 
Hope that helps.

Distortion with just guitar sounds a lot like you are clipping the signal at "some point" in the signal flow. I installed pickups that claim to be the hottest passive pickups made, and it was not until I ran it straight into my audio interface (medium gain) and used the digital meters in X3 that it was obvious how much extra gain was on the low E (like 12 dB hotter). Pickup height and gains are something else to check.
 
In my case, variations in play triggered it, but it was obvious where it was happening. This post is more detail on how I pinpointed and adjusted them.
 
Weird gains causing distortion/clipping are very common with things mentioned in this thread already (electrical interference, cables, corroded connectors/switches/pots, pickup height). Isolating things individually helps... even simple things like cycling switches/pots on guitars and amps are often needed to wear off excess corrosion on them that can cause the effect you are seeing.

Yeah, I think this distortion matter is solved with some discipline in your performance. Don't play so loud at the points where the distortion is happening, and, alternatively, if you're recording the guitar by micing the amp and running the mic into the input of the audio interface, maybe positioning the mic farther away from the amp may help.
 
Let us know how it's going with you

When I record guitar, I've been setting the Volume on the interface to where the meter reads just over half way.   That's not even near clipping.   
 
The pickups on my guitar are not the issue.   It distorts with low wind single coils.   The bridge humbucker is 8.9k, and I have it backed off the strings probably a bit more than I need to.   My amp is not a high distortion amp.  And I don't play with a lot of distortion.  
 
Last time I recorded I used 2 mics - a Sennheiser e906 and an Audix OM2.    Both sounded the same.
 
This is a clip of me a couple of years ago.  The guitar sounds really good, I think.   I am doing nothing different in how I'm recording now, but the results are not the same.  
 
https://soundcloud.com/greg-williams/short-clip
 
Thanks!
Greg
 

So when you record: you mic your amp with your mic's?
 
How does it sound if you try to sing in the mic's? 

I've done vocals for all of my songs, and everything sounds fine - even acoustic guitar.    It's just the lead guitar.   When I record with a little distortion, that's when I run into trouble.   I've had my amp serviced, and everything checks out and sounds great.   I'm using the same equipment (except for computer and interface) that I've always used.  
So this is strange...
 
Greg
 
 
 

I hate to say this but if you had the title" Guitar track distorting" instead of CPU issue you would have had some solid solutions right away. Your computer has nothing to do with distorted audio tracks. Distortion ONLY happens when you clip an audio signal. This can ONLY happen in the audio signal chain BEFORE it reaches the computer. When you arm the track in Sonar, what does the track meter show? 
If this is good then the only other conclusion would be the interface pre amps or A/D is acting up. 

Cactus Music
When you arm the track in Sonar, what does the track meter show? 
If this is good then the only other conclusion would be the interface pre amps or A/D is acting up. 

When I arm the track, everythng is good, like it's always been.   I've been recording not as long as some, but long enough - about 11 years.   
Everything checks out fine when I record, but the guitar doesn't sound good in playback.  
Thanks!
Greg

I listened to some of your Music yesterday. It sounds good.
 
My last four posts contained some good troubleshooting info. You didn't answer any of the question. Did none of those suggestions help at all (see posts #34, #40, #41, and #42?)
 
Again I say, if you use a more appropriate title, such as "Guitar Audio Distorts Please Help?" You may get better assistance. There are a lot of forum users who work with guitar recording and know SONAR and computers very well. I don't work with real guitars at all. So re-titling this thread or starting a new one with a better title for guitar distortion help may be more beneficial for you.
 
To me it really does sound like a problem created by playing loud at points where the audio distorts (because the distortion is only heard on part of the guitar track and you can record vocals without them being distorted,)  a mic placement problem for recording the amp, or a mic preamp problem, again have you tried turning the Hi Z setting on the back of your interface on and off when you record? One of those Hi  Z settings could mean you are bypassing the preamp on the audio interface and recording directly at Line level.
 
Do you have a small stand alone preamp you could use or another audio interface to test with?