I agree with @mulveling. The Blue Velvet is a real bottleneck. It floors me to see otherwise respectable preamps with a Blue Velvet. It is a genuine loser. I first tried the Blue Velvet about 25 years ago and didn’t like it. I then bought an Alps Black Beauty and I loved it. That led me to order a number of pots to see if I could find something even better than the Black Beauty. These included Noble, TKD, a stepped Alps, vintage Allen Bradley, a couple stepped attenuators, and an expensive Penny and Giles. None of them sounded as good as the Black Beauty so I bought a few spares. Two decades later they still sound just as good and they are just as quiet as they were when I first installed them. Definitely a good investment.
The Alps RK50 is supposed to be even better than the Black Beauty. I have never heard one so I don’t know that for a fact. In any event, they are not only hard to find they are also quite large, too big to fit in my main linestage. However, if I do come across an RK50 I will try it just to find out.