A little bit late, but better than never
Im a recording and mixing engineer. As time goes by i get more and more stuff to mix that people created at home, or finished overdubs at home after recording elsewhere. Needless to say that most use very basic setups that creates a challenge when mixed- chinese mics, soundcard preamps, you name it. add to that poor mic placement, and so.. harshness doesant always comes from 'digital sound'. But there are some ways to diminished that.
I would suggest what others did- build yourself a tranfer chain that you are happy with. There are a lot of good analog gear these days that doesnt break the bank to buy. I would suggest a good quality preamp that goes to eq that goes to comp. That way you can control and warm things before capture.
Hardware Tape sim is also to be considered. Then for conversion theres multiple options- from colory like Burl to a more natural like Symphony. I believe that with these tools you wont get an undesired harshness in your tracks. And any minor details can be treated in the digital domain afterwards.
As to that, earlier on this page i saw that someone wrote about frequency notch sweep as a method.
I do the same but the oposite- i use protools eq solo function, which is dimnishing other frequecies ranges beside the one that is soloed, and not notching for positive values during that process. That way you can adjust the finest details for the program materials as well as fx returns and sidechains through your tracking period without any unwanted frequecy/energy through that process.
I use plugins deessers, tape sim and summing sim alot to tame the highs the way i like them. Alot of time i put them first and starts playing through them, balance, and starts the mix process when every element is aligned and 'sounds right'. Its getting better every year and for a few years i feel that the gap is closing and its hard if not impossible to identify an ITB to a full analog mix. Its much more depends on the ears that makes the calls then to anything else.
Have a great weekend,
Avraham