Dude's 6SN7 replacements with Chinese CV-181/6SN7

I have not tried those, but use 1940's RCA smoked glass and love them. Andy at Vintage Tube Services is the place to buy NOS RCA's.

Let us know if you try those CV181 tubes!

I've had both in my system. If you try the Sophia, you will love it. Very open and neutral. But when you try the BT CV181, you'll be selling the Sophia.
Just go to Grant Fidelity and get yourself a pair and you'll be glad you did. I have no affiliation with Grant Fidelity, I'm just a very satisfied customer.

While I can't speak to the "Dude" preamp, I have tried both the original BT tubes and the Sophias, (and many others) in my Modwright LS-100 preamp. I am using a Mullard GZ34/5AR4, (Blackburn) as the rectifier.

Each pair need a massive amount of burn-in/break-in. Grant Fidelity recommends 150-300 hours for the BTs. I have over 500 hours on each pair.

I find the BTs to be my "keeper" tube. In my system and for my tastes they throw a wider, deeper soundstage and are smoother and more open than the Sophias. I think that the Sophias are "a tad" more neutral, linear and have more detail, but that's not what I am looking for. I wanted a smoother, more open, more romantic sound and found that in the BTs. Had I started with the Sophias, (I didn't, I started with the BTs), I might have just stopped.

Bottom line, they are both excellent tubes and really need to be tried in one's system to match personal tastes and preferences. You really can't go wrong with either.