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. 


Just a follow up of using the tube buffer with the PRE90. I changed the stock Tungsol tube to an Allen 12au7 and the noise floor is dead silent now with a nice balanced sound. So you can have your cake and eat it too! I have a Psvane Art series 12ua7-s on the way to compare. Let's see what it brings to the table?

@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.