Craig,
 
Item 1 (use double rates to avoid fold over) in the article you link above isn't needed in Sonar these days because of the cool 2x button, right?
 
When you mention limiting, tip 4, I think of people who chop the guitar. Stiff compression around the level just above loud melodic play. This tip could work well on Mandolin too. There's an instrument that is usually chopped almost twice as loud as the melodic work at the breaks.
 
I've been trying to teach the musicians to back off the mic when chopping and then get up on it for breaks, but a nice limiter/stiff compressor might really help the live sound.

Anderton
If you're looking mostly for clean sounds, you may find this article helpful.

many thanks for the useful info. However it doesn't help in this instance. The problem appears to be that TH3 requires an input signal which is too hot. the di'd signal is already in the red and since TH3 only provides output control there is no way of moderating the input signal. The sound I hear when playing is not the sound I hear recorded, the recorded sound has way more distortion, as you would expect from such a hot input level.

chudson.  Can I ask you a few questions?  When you say the sound I hear when playing is not the same sound that is recorded how are you playing it?  Do you have input echo turned on in Sonar so that you are playing TH3 as a VST plug-in through Sonar?  When you record are you recording the output of TH3 into a track or are you recording the direct signal?  If you are recording the direct signal can you listen to it with TH3 bypassed to see what it sounds like?
 
Something doesn't sound quite right to me and it seems like we have not quite got to the bottom of your problem.

chudson

Anderton
If you're looking mostly for clean sounds, you may find this article helpful.

many thanks for the useful info. However it doesn't help in this instance. The problem appears to be that TH3 requires an input signal which is too hot. the di'd signal is already in the red and since TH3 only provides output control there is no way of moderating the input signal. The sound I hear when playing is not the sound I hear recorded, the recorded sound has way more distortion, as you would expect from such a hot input level.

I recall having this issue some months ago.  My various DI options couldn't provide an input that was "suited" to TH3 according to their "adjust input to the correct level" instructions. 
 
I found a solution, but was kinda expensive.  I added a outboard (SSL) preamp to my rig.  It also acts as a fine instrument input.  With the new pre/DI, I was able to get the input graph into the "good space". 
 
When I saw this thread I did a quick recording, and I do hear a match between monitoring/playback.
 
I'm no expert, but you may have better luck if you can add some juice to your input signal.

There Is a gain knob on every track. Is the gain knob at zero?

Do You experience this if you create a new project?

I use TH3 all the time and my sound while recording is identical to my sound for playback.

gswitz
There Is a gain knob on every track. Is the gain knob at zero?

Do You experience this if you create a new project?

I use TH3 all the time and my sound while recording is identical to my sound for playback.

interesting to hear that you aren't experiencing the same thing that I am, doesn't actually fix my problem but is reassuring that it could be something I'm doing incorrectly rather than TH3 not behaving.
 
In response to your questions the answer to both is yes.
 
to give more detail and to reply to rginald Stjohn, here is what I've done so far and the steps:
1 - create new empty project
2 - create new audio track
3 - set quad-capture audio interface level, signal in sonar at around -6db
4 - add TH3 guitar audio fx into track effects bin
5 - select blackface amp and default cab
6 - play guitar :-)
incidentally its a Les Paul, I have the master settings in TH3 set to have In source set to left and sensitivity to high all other settings as default.
7 - sound 'live' is weak, almost uneffected by TH3 - input is too low for TH3
8 - increase the input level on the quad-capture to accommodate TH3
9 - sound 'live' is now pretty much as you would expect from the simulated amp/cab set up however signal in sonar is now way too hot (all red even when playing gently)
10 - record guitar playing
11 - recording is distorted, especially on the low end
 
couple of other things to note:
quad capture has a simple mix nob which enables the mixing of input and playback signals - I have this set to all playback and no input signal so what's comin out should be only what's being sent out by sonar.
 
I have tried this through both speakers and headphones and the result is the same.
 
I have no other tracks, plugins, pro channel modules just the bare track
 
I have also tried recording the input track at the -6db level and then routing to a bus with TH3 in the fx bin on the bus and boosting the source track to try to push the input to a level that TH3 would be happy with - just weak sounds again.
 
One thing that does occur to me is that all of the online demos and reviews demonstrating great sounds all seem to be using the higher gain/distortion models rather than clean sounds. Is it perhaps just a case that the TH3 clean models are not up to the job?
 
I have used the higher gain sounds and get good results but I suspect that this is because these are less affected by decreasing the output levels than clean sounds. lowering the output level from TH3 on driven sounds just seems to make them quieter whereas lowering the output level on a clean simulation kills all of the dynamics.
Finally I have Cakewalk TH3 edition that comes with sonar platinum and no add-ons.
thanks again
Colin

https://youtu.be/23oF5jGq1pk
 
idk if this video might help you at all. I figured it'd be worth a try.

I believe what Colin is referring to is the TH3 instructions which require setting the TH3 input meter into the green for optimal gain as designed.  I tend to like to record with peaks around -10 to -12, so as to maintain some headroom, but this keeps the TH3 meter below the green.  When you then set the TH3 meter into the green (no input control, you have to use your preamp), it clips Sonar's input meters.  I have both Guitar Rig 5 and Waves Guitar Solo and they both have internal input and output control.  But IMO, TH3 when set properly, sounds better than the two other plugins I have.  But gwitz's suggestion may be a solution, because the pro channel chain has separate input and output controls.  This should allow you to set optimal recording level into the Sonar and then adjust TH3's level with the pro channel chains controls.  Thanks for the video gswitz, completely forgot about the pro channel chain; going to have to try this.

Peli,
The Gain knob on the track is also applied post recording. you Could use this to set input gain heat into TH3 the same as FX chain input gain.

When You use FX chain input gain, the pro channel clip indicator can caution you to an over driven signal.

https://youtu.be/r0hqNPpvmIU
 
A video trying to show those ideas.