SC-05-05 meeting, Online, 2023-10

Report of the meeting of the SC-05-05 Working Group on Grounding and EMC Practices held online, 2023-10-09

The meeting was convened by Standards Manager Rich Cabot.

In attendance were Richard Cabot, Jim Meyer, Kenneth Fause, David Prince, Fred Morgenstern, John Celli, RJ Kenney, David Andrews.

The formal notice on patent policy was read.

The meeting agenda was accepted as written.

There were no minutes of the previous meeting held online, 2023-05-03.

Projects assigned to this group but not mentioned here had no action requested or required - see for details.

Open Projects:

AES-X152: AES standard on interconnections - Audio interconnection specifications
SCOPE: “To develop a standard for presenting signal levels and circuit impedances of audio system components and for the specification of these quantities in product data sheets” The goal / target / deliverable is a datasheet template that manufacturers could include in their manuals that explains the characteristics of the signals leaving devices and the characteristics of signals a device is capable of receiving. Having these parameters summarized in a consistent way will help users integrate equipment.

The chair described a recent idea for characterizing how output interfaces behave. Previous approaches required the manufacturer to disclose the technology used in their device and required the users to understand how the technology would cause the output to behave in their application. The proposal is to measure the output voltage on each side of a balanced output using two different test loads. One load representing a typical balanced input, for example 5k Ohms from each side to ground. The other load would have 5k Ohms on the high side (XLR pin 2) and a low impedance such as 500 Ohms on the low side (XLR pin 3). The concept was well received. Jim Meyer proposed something similar to the group in February of 2021. His proposal is in the document repository.

The group needs to develop a procedure description which implements this and to determine the preferred load resistances.

After much discussion it was suggested to lower the 500 Ohms to perhaps 100 Ohms.

It may be necessary to also perform a measurement that detects whether the low side includes a dummy impedance vs being tied directly to ground.

AES-X249: AES standard on interconnections - Grounding and EMC practices - Shields of 25-way D-type connectors in balanced circuits
Whether the shield of a multichannel snake cable should be grounded, and if so, where was discussed in detail. An informal survey conducted by Fred Morgenstern showed that industry practice is to leave it unconnected.

New Projects

No new projects were proposed.


No liaison activity was reported.

New business:


The next meeting will be scheduled in conjunction with the AES 156th Convention, to be held online in May 2024.

AES - Audio Engineering Society