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. 


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. 

@rrboogie I look forward to hear your impressions of the Yaquin with the Pre90.

I did notice that the s/n ratio is listed at greater than 75db for the Yaquin. It seems it may be too noisy for the super quiet Pre90.

 I am hoping that it is not too noisy as well. My idea with that unit is to have a little more "tube flavour", midrange bloom so that I could switch between the two tube buffers for a different listening experience. I am contemplating purchasing an ifi itube2 on the used market. Much better S/N numbers at 119dB.

I sold the Pre90 and bought the A90 discrete for it’s added headphone capabilities which are fantastic with my Hifiman HE 1000v2 headphones. The A90 discrete sounds a bit warmer to my ears in comparison to the Pre90. In the last couple of months I have A/B it against the Border Patrol EXT 1 and the Rogue Audio RP-7 and decided to keep the A90 Discrete in my system along with the ifi itube2. The Yaquin buffer sounded too dark, lacking details. The Jolida SSX got beat out by the itube2. I do prefer the tube buffer in front of the A90 Discrete but only by a slim margin. I could live happily with the A90 Discrete without it as well but I hear a little more presence, body and 3D soundstaging with the tube buffer in the chain.