Topping Pre90 Switching op amps?

I am running the Topping PRE90 with a VTV Purifi Eval 1 and I agree with your assessment regarding it be the incredibly transparent to the source but can sound thin or brittle. I remedied that with a Jolida SSX tube buffer and it renders the music with more body and tightens the bass. It's the best my system has sounded. Maybe this might be a direction for you rather than swapping opamps.

@dbb Surprisingly, it did not not reduce the transparency. I can still hear all of the details. I am using Altec A7 speakers which are over 100db efficient and it added a slight bit to the noise floor but you need to put your ear up to the treble horn. Preamps I had before this were Pass Labs X1, Modwright LS 36.5, Black Ice Audio Fusion F360. All had a higher noise floor. I tried the Topping D70s direct which was excellent on it's own and lead me to the PRE90 which on it's own is dead silent. 

The remote is weak. Not great off axis. I use an infrared repeater and it works great!

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?

I use the ICESPRING unit bought off Amazon and it works for me. YMMV

@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. 

 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.