JJ Has this right. Cardas sold a few of his own versions of a mic with the capsule. I never heard one or saw one.
David is one of the brightest minds in mics around right now and turning him lose to design a new benchmark with such a unique capsule seems like a winner. The first implementation of a mic with the capsule was the Bock 308 targeted at a flatter response. The Bock 507 shoots for a different target, "big vocals", as its the one most people are looking for. A big vocal mic that isn't too bright is hard to find outside of vintage. I'd like sometime to have a version that does both 308 and 507 functions in one mic (508??) on a switch. But one step at a time!
Contrary to some posts in this thread, the 507 is much more than a capsule. Its a unique blend of tweaks in the amplifier, the custom transformer, the head grille shape, wire, power supply, etc, etc. Saying its all about the capsule (like you hear people say its all about the tube) sells the whole project short. This is a "build the best on all fronts" effort. In that regard, its much the same thing we asked Klaus to do with the KHE. Turn smart people loose, great things happen.
Brad