Interesting.
I’m still somewhat lost (story of my life, I guess … 
).
Just to be clear, you are using an actual mono input and not 1/2 of a stereo input for the stereo audio track?
I’ll have to do some experimentation later when I get a chance. I haven’t been using AmpliTube much lately and I can’t remember the last time I tried the standalone. However, in the past I have never experienced any shortcomings using it as an insert on a stereo audio track with a “true” mono input bus.
Okay, I just spent some time jamming in AmpliTube standalone. Saved a preset I was happy with and closed the application. Opened Cubase 12 Pro, created a stereo audio track with a mono input. Added AmpliTube as an insert and applied the same preset. Can’t tell any difference. I still don’t know what you folks are talking about.
I don’t know whether it is my version of Cubase at this point.
Let me guide you step by step:
TEST #1
Create a STEREO input BUS with only the left channel connected to a physical MONO input of your soundboard.
Then put AT as an Insert on the INPUT TRACK, not on an audio track or on a group track - I truly mean directly into the INPUT track, which is a STEREO track associated to the stereo bus you created in the step above.
Now look at the input and output meters in the UI of AT: only the left channel is animated in the input, while both left and right meters are animated in the output.
This happens because AT is working in STEREO mode because it is on a STEREO track; though only the left channel is fed as input. This makes the overall input gain lower due to the pan law (see Pan Law on Wikipedia for reference, I cannot include links in this post). Therefore the algorithms of AT sound worse than at full gain, despite AT is producing a stereo sound from a mono signal.
TEST #2
Create a MONO input BUS and bind your mono physical input on the soundboard.
Then put AT as an Insert on the associated input track. That’s a MONO track now and AT will work in mono mode. Open AT, and you’ll see both meters of the input animated at unison, as if it was a dual mono input signal. The output meters behave at unison as well, because that’s NOT a stereophonic output.
Now play your guitar and pay attention to the sound AT produces: gain is a little higher (3 dB higher, to be precise, due to the pan law) and the overall dynamics are better compared to TEST #1, especially when you have distortion/crunch.
I’ve been using Amplitube for years. Never ever have I noticed anything like what’s described by the OP. There must be some other funny business going on in a project like that. Are your panning set to center for any stereo pairs?
You are really overcomplicating things. Why do you want to insert AmpliTube directly on the input bus (there is no such thing as an input “track”)?
If you use it on the audio track insert and record your dry signal, you have limitless possibilities to go back and tweak things after the recording.
The methods of operation you describe could, indeed, produce the results you have found. I’m not going to test them because … well, they just don’t make sense to me.
Anyway, you know how to make this “work”. Keep doing things in ways that others would not if you want complications, I guess.
But why would you put a guitar on the left side of a stereo bus?
You can create a stereo audio track, connect the input to a mono bus. Done. The track is stereo, you have a single waveform on it when you record. Still like it hotter? Give it 6 dB from the PRE section gain.
Having a stereo track configuration, and a stereo bus configuration, and recording one side of it only (you see two waveforms when you record, one is a waveform, the other a straight line)… well, it sounds kind of crap, to me.
Dimitris_Patrikios, did you ever find a solution? I’m having the same problem, sounds very harsh and thin, compressed and muddy" in both the Standalone Version of Amplitube 5 and through my Cubase Elements DAW. I’m about ready to just give up and move on. If you don’t mind sharing your thought on this, I will be eternally grateful. Thank you!
Not Dimitris, but most often than not, I’ve found that most plug-in emulations (Amplitube included) are very sensitive to the signal’s input level.
Between different sound interfaces and pickups, it’s very difficult to offer specific advice. Make sure that the Audio Track where Amplitube sits on is stereo (for modulation effects, reverb etc), BUT that the input chosen is Mono. (Where you have plugged-in your guitar)
And then it’s a matter of carefully adjusting gain, so that amps and effects respond naturally. For me, it’s on the low side. I don’t need a very hot signal for this. If I crank up the gain, it sounds harsh.