musical fidelity tube buffer

I added this tube buffer to my system when I found it a bit fatiguing, and hoped this would smooth out my CD/SACD player.

It is nicely made and nicely packaged, easy and fun to use.

This perhaps contributed to more of a placebo effect improvement, as other threads have suggested the benefits are not extraordinary and depend mainly on the source.

Now, I am experimenting with it as a buffer between my PC using Apple Lossless files, a cheap USB to RCA interface and active monitors on my desktop.

Would anyone know what source devices would be most likely to benefit from this device?

It may seem like an anathema, but has anyone tried pairing one of these with a passive line stage?

You should note that the MF buffer has only unbalanced inputs/output and may be an issue if you are using balanced connections with the BAT preamp. I use the buffer between my Arcam CD23 and Placette active line stage (using VD Nite interconnects) and it sweetens the midrange a bit. Also makes the sound a bit easier to listen to...less digital. Music Direct has a good return policy and I believe that unit is on sale right now.

Given the level of your electronics, I personally would not want to run the risk of mucking it up with the (relatively) cheap (esp used) tube buffer. I'd think about selling the preamp and buying a tube one same brand/same price range.