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.
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.