I see two problems with the way Phędrus advertises its 6D-H3:
1. It is not a tube, as soapfoot stated, but a solid-state emulation. I find it troubling that a manufacturer refers to a solid state device as a tube and uses terms germane to tubes ("heater voltage", "triode", etc.) when the common definition of a tube is, per Wiki:
A vacuum tube or electron tube is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied.
It utilizes thermionic emission of electrons from a hot cathode for fundamental electronic functions such as signal amplification.
2. This solid state device is advertised as a direct replacement, therefore claimed equivalent in performance, to the AC701 triode.
All tube emulations I have heard, including those made by Phaedrus, sounded pedestrian to me. They will pass common function tests with more or less noise associated with it, and may be ok for beginners not familiar of the timbre and dynamic behavior of tubes. I.e. a perfect starting point for DIY's.
But there are better and cheaper alternatives in that category, like the 6S6B, a Russian military type triode tube. (Neumann uses what looks like a relative of that tube in its M49V.)
In the end I question the idea of installing a tube simulation in any of the most revered, iconic, breathtaking mics ever made- those originally designed and optimized for the Telefunken AC701.
Knowing your excellent ears and discrimination for good sounds, I encourage you to buy one of these simulations, install it and report back with what you hear.
P.S.: I also invite anyone who has personally heard and compared solid-state emulations to post his/her experiences.