The meeting was convened at 10:30 by acting chairman B Olson.
Attendees introduced themselves, Present were M Natter, P Treleaven, B Olson, A Klingelnberg, R Cabot. A signup sheet was circulated.
The formal notice on patent policy was read.
The agenda was approved after the addition of AES48 to the New Projects section.
The report of the previous meeting, held in New York, 2017-10-20. was approved as written. The chair reminded everyone that he is temporary and that we are soliciting people to become permanent chair and vice-chair.
Editorial Note: Most of the work is done via electronic means between the meetings at conventions and that people can participate or even chair bi-annual convention meetings remotely. If anyone is interested in chairing the group they do not need to be able to physically attend the convention meetings.
Projects assigned to this group but not mentioned here had no action requested or required - see www.aes.org/standards/meetings/project-status.cfm for details.
AES-X152: Signal levels and impedances of analog audio interfaces
Scope: To develop a standard for signal levels and circuit impedances of audio system components and for the specification of these quantities in product data sheets [balanced, unbalanced]
Discussion: This topic will be tabled until there is a permanent chair.
The current draft document was posted in 2009 and should be reviewed by the new chair and the group via the reflector.
No activity to report.
As was discussed at the previous meeting in NY, the figures in AES48 imply that all circuit ground currents should be routed through a common point to chassis. If this is applied to ground currents from EMI filtering components on I/O connectors it will completely negate their effectiveness. R Cabot showed some modified drawings which clarified the difference between signal and EMI ground connections. The main point of AES48 is that cable shields should be connected to the product enclosure with the lowest possible inductance. The diagrams illustrate that any EMI filtering applied to a cable connection should also return current to the same connection point as the cable shield with the lowest possible inductance.
There was considerable discussion of the practical aspects of these principles. There was also discussion of the process required to bring AES48 out of stabilized status so that it may be modified to eliminate this confusion.
R Cabot agreed to upload the figures to the document site.
The next step must be to draft a project scope, create a project initiation form and return AES48 to active status.
A Klingelnberg raised the issue of common mode impedance vs differential impedance and whether those could be specified for connections. The chair described some journal papers which discussed this issue. He also mentioned that this is discussed briefly in AES54. If there is sufficient interest the chair was receptive to starting a project to describe and document these topics either as annexes to existing standards or creating a new information document.
The meeting closed at 11:30.
The next meeting will be scheduled in conjunction with the AES 145th Convention, to be held 17 to 20 October 2018 in New York, NY, US.