SQ impact from a tube preamp after signal leaving an AVR?

emergingsoul, the AVR itself is the signal quality impact.

Ditto what millercarbon said, re-read his last two sentences again, "G-D" right.

You can't add information, but that does not mean you won't prefer the sound after adding a tube-pre.  I wonder if other responders have ever worn sunglasses or used an equalizer and liked the results?

Funny, good analogy and pivot.  And, no use of sunglasses or equalizers in the house here. Later learned how much more we could see and hear without them.

Oh the memories. Messed with a number of ADC, SoundCraftsman, Sansui crossovers in the 70s and 80s though. Kinda like this one.
https://i.etsystatic.com/15730567/r/il/8d1564/1542010526/il_1588xN.1542010526_7smm.jpg

Must say though, if I needed or wanted an equalizer today, this little Schiit Loki is pretty cool for $149
https://www.schiit.com/public/upload/general/loki-mini-front-1920.jpg

This horse has been bludgeoned to death already by the OP who seems obsessed with asking the same question from as many redundant angles as he’ll continue to get answers for.  Enjoy the insanity people.  Peace out. 

So the merits of higher priced tube preamps may be in doubt.  The absurdity of buying overpriced components.  Yet we do it.