That little plug-in is a Pro Channel fave of mine, salt to taste and it adds a little extra dimensional quality to things especially on a stereo bus.
 
The good news it's available as a free standalone vst3 plug-in:
 
https://www.softube.com/?id=news78
 
The bad news is you need an iLock. I know some people hate that, but I have one from Pro Tools and Drumagog so it was no big deal for me.  
 

That ridiculous huge space-disrespecting knob has to be the most useless ProChannel-plug ever.
 
There are soooo many distortion effects!
 

https://klanghelm.com/contents/products/IVGI/IVGI.php
Free, no ifock
 

It's big brother is Sex, Drugs and Rock and Roll, oh, and just 23 Euros, which is nuts cheap
https://klanghelm.com/con...products/SDRR/SDRR.php
 

https://klevgrand.se/products/squa****/
On sale $17.99
 
 

It works as a standard VST now - I pointed Sound Forge's VST folder at the SONAR Internal folder and this (and 2 console emulations which won't work outside SONAR) appeared and worked.

Also comes free (Softube) with Presonus Studio one 3 Professional as a free download from the Presonus store.

I just read the link for the free softtube knob and it said:
 
No iLok is required for using the Saturation Knob. For any of the other Softube plug-ins in the installer package, iLok owners can download 20 day demonstration licenses.

emwhy
 
The bad news is you need an iLock. I know some people hate that, but I have one from Pro Tools and Drumagog so it was no big deal for me.  
 

 
You wont need a physical key, but you will need an iLok account.
 
The Saturation knob can also be used within Modular (Softube's VSTi Eurorack modular synth). Here it is very useful, I like to put between the oscillator and the filter and "voltage control" the saturation setting for interesting harmonic modulation effects. I must admit, as much as I like it in this scenario I have not used it much in the pro-channel or as a VST effect.

I route all my drums to one subgroup/bus before sending to the master bus.  If I patch the Softube knob in the chain on the drum subgroup before the limiter I use or console emulation and turn it up just a touch so there's no distortion it gives me a nice little something extra. I have external tube mic pres in my rack and when saturated just right the audio has a more 3d quality to it if that the sort of thing you're after compared to the pres on my interface.  The Softube knob gives me something similar inside Sonar.
 
 

jpetersen
That ridiculous huge space-disrespecting knob has to be the most useless ProChannel-plug ever.
 
There are soooo many distortion effects!
 

 
And just how few versions of an effect must there be before you don't consider it a waste of space? I guess every EQ and compressor is a waste of space as well? 
 
As far as saturation plugins, they're not all the same. Some are better than others. The Softube saturation knob is very good quality, so is hardly a waste of space.