Topping Pre90 Switching op amps?

I have found that the pre90, in my system, renders many recordings beautifully transparent and many other recordings thin and brittle. It seems that swapping op amps might be a solution. Has anyone done this? If so kindly report on your experience. 


@kr4 If this is Kal, I purchased a Topping Pre90 to replace a Schiit Freya (with tubes) based on your writeup in Stereophile. Love it. Yes, one does need to be a marksman when aiming the remote!


It is I and I really wonder about adding a "tube buffer" to the Topping.  Seems counterproductive.


@tomcarr ​​​​@kr4 I also replaced the Schiit Freya + with the Topping Pre90 with the Jolida SSX. I had some local audiophiles over and we A/B'd them and everyone picked the PRE90 and Jolida SSX over the Schiit Freya +. I just sold the Schiit Freya + and have a Yaquin SD- CD3 Tube Buffer on the way to compare as I have a good stock of 6SN7 tubes to roll in it. I'll report back.