I hadn't heard David's latest version of this mic, since he switched from using the 6072 tube to the 5670, so he lent me one recently to check out. Goddamn. If you need a 251, and don't want to spend $20,000, this is the one I'd get. Honestly.
Listening to it against a mic that he built for me using a NOS CK-12 capsule, 5 star GE 6072 and a TAB built T14/1, and a mic that consists of a Tele USA body, yet everything from the capsule down to the resistors is vintage AKG, I'm so impressed that he managed to keep that great sound in the new revision, even with changing to very big components.
I can only assume that a great deal of work was done with Oliver at TAB, to make sure the custom transformer delivers the tonal balance in combination with this tube, that the 6072 and T14/1 combo gives you.
The reason for the change is simply the fact that usable 6072s are scarce, and expensive. David's philosophy is that it would be bad business to build a mic, for which he can't supply first rate replacement tubes in the foreseeable future. He searched for a tube that was high quality, that he could get in sufficient quantity, and bought himself a truck load of 5 star GE 6072s. Other companies are either selling mics with inferior 6072s, or they are using an outright different tube altogether, which completely changes the sound of the mic, when paired with the T14/1. This brings up problems of noise and getting away from that vintage 251 sound.
Having heard a few of his custom built Haun CK12 type capsules, I can say that they certainly have tighter tolerances from one to the next than real CK12s. I have a lot of CK12s, including a couple NOS ones, and I've borrowed a few to test, and even though they all have a similar hallmark, they are all over the place, even within the same revision. There is a much more uniform response to the Bock capsule, from one to the next.
However, my very favorite CK12 has a little more sibilance and air to them, than the Bocks. That being said, I have had a chance to personally test the AKG CK12 that David based his capsules on, which he deems as his favorite, and the high end of his capsules are definitely modeled after that one. Nonetheless, his capsules certainly fall within the sound of what I think of a really good examples of CK12s.
But that frequency response comes down to a question of taste, and I find that not everybody likes those high frequencies the way I do. In fact, while they can make some voices sound magical, they can make some unlistenable, and perhaps it is better to uniformly go for the less brighter option. It makes the mic more universally usable. None the less, on a singer such as my girlfriend, who is all about soft, throaty air, this mic sounded every bit like a 251, in capturing the air, and the texture, while still delivering sparkling mids. In fact, I had her do takes between my Bock with the vintage parts, and this new one, and I will be comping between the two, without anybody ever noticing, I assure you.
There are several people making 251 type mics, but I have been saying to people for some time (and this only reinforces my impression),this is my favorite one. Also, I love knowing that there is a real microphone genius on premises, who is designing, building and testing the mics himself. The craftsmanship, part selection, and attention to detail, puts these mics at the top of the class, as well.
And for the benefit of Google:
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