The AES42 standard has created a bit of an odd situation. As you can see from Neumann's product lineup, it isn't hard to power
one microphone at a time and derive either an AES/EBU or S/P-DIF signal from it. That's great for the project studio people who only "track" with one microphone at a time.
But for those of us who record in stereo using 2, 3 or 4 microphones at once, there's a bit of a problem: Each digital microphone contains its own clock circuitry, so no two are exaaaaaaaactly alike. Thus when more than one microphone at a time is being used, one of two things must occur:
(1) The signals from the microphones must go through a process of asynchonous sample rate conversion so that the signals they deliver can be recorded synchronously, or
(2) The clocks in the microphones have to be nudged into conforming to an external master clock.
The AES-42 standard has an extremely ingenious way for approach (2) to work. The interface which powers the microphones observes their exact data rate, and advises them (via a flag in the bitstream) to slow down or speed up until everything is properly in synch. In my opinion that is distinctly preferable to any asynchronous sample rate conversion.
Unfortunately, however, the only free-standing implementation of this approach that I know of is in Neumann's DMI-2 interface, which currently lists for $1,418.00 in the United States. I assume that the powering and synchronization could be implemented for less than that, but probably not very easily.
A courtesy PDF copy of the standards document can be downloaded at no charge from the AES' Web site. See
http://www.aes.org/publications/standards/ .
By the way, as someone else mentioned previously, Schoeps' digital microphones work just fine with Neumann's powering adapters--one advantage of having such a standard, and of manufacturers who treat such standards with appropriate respect. Schoeps doesn't offer any powering devices for digital microphones; they anticipate that this facility will be built into preamps, mixers and recorders in the not-too-distant future.
I personally am in no great hurry to convert to this approach, since its advantages in my type of application are so minor compared to the costs. If the advantages increase or the costs decrease, that will tilt things a little differently. For me, for now, I don't find that the analog interface limits my ability to get a good recording when my mikes are in the right place at the right time.
--best regards
Topic: digital mics (portable AES 42, schoeps, neumann) (Read 11711 times)