The agenda and the report of the previous meeting, held in Paris, 2006-05-21, were approved as written.
Finally there was discussion about whether to extend AES42 to incorporate other digital microphone interfaces such as USB or Firewire (IEEE 1394). There was consensus among the WG members present that while SC-04-04-D might well be the appropriate task group to address these issues, they were distinct from AES42 and should be handled as separate projects, AES42 being a single defined interface.
S. Temme (Listen, Inc.) and P. Pegas (Audio Engineering Associates) were added to the SC-04-04-E task group for development of test methods.
The first sample of the reference noise source produced by DPA Microphones appears to have been lost in transit, and DPA has produced another example which will be tested in turn by each of the members of SC-04-04-E beginning with Listen, Inc, then to AKG whence it will proceed in the same order as the microphone samples did in the earlier round-robin tests. Each participant will measure and report the A-weighted rms noise and psophometric quasi-peak noise of the noise source, and its noise spectrum, and report to the Working Group. M. Opitz of AKG will tabulate the results as they appear on the email reflector, as he did for the microphone measurements.
There was no consensus on the method to be used for reporting noise spectrum, several options being possible. One-third octave noise bands probably present the most useful and readily comparable metric for this characteristic.
AES-X093 Recommendations for Revisions of IEC 61938 Clause 7
The 2001 PWD of an Information Document on a revised phantom power standard was revised to incorporate concerns raised since it was written, and is now released by its writing group to the Working Group. It will be discussed over the next months, with a goal of voting on its acceptance as an Information Document at the next meeting. This information can then be passed to IEC TC100 as AESSC's recommendation for the revision of the IEC standard.
The basic change is to adopt 7 milliamperes as the "typical" maximum current, with the note that this value represents the maximum power transfer that is possible with standard P48 current limiting resistors. There is also support for noting that P24 phantom power is deprecated, perhaps using stronger language than the proposed "not recommended for new designs." It is understood that the present language in IEC 61938 (Ed.1 1996-12) preferring P24 may have been incorporated in error.
The IEEE standard exists and is in wide use; the AESSC's proposed role is simply to define its implementation for microphones a bit more clearly. There is a good possibility that this may become an alternative to phantom power where a low cost unbalanced powered interface is desired.
The next meeting will be scheduled in conjunction with the AES 122nd convention in Vienna, Austria, 2007-05.