Sound system interconnections and grounding

Rane Sound System Interconnection note, originally written in 1985, continues to be a very useful reference. It’s popularity stems from the continual and perpetual difficulty of hooking up audio equipment without suffering through all sorts of bizarre noises, hums, buzzes, whistles, etc.– not to mention the extreme financial, physical and psychological price. Many things have improved in the audio industry since 1985, but unfortunately wiring of analog signals isn’t one that has progressed much.

In 2005 Audio Engineering Society (AES) issued a standards document for interconnection of pro audio equipment in AES48 standard: “AES48-2005: AES standard on interconnections — Grounding and EMC practices — Shields of connectors in audio equipment containing active circuitry.” The standard was reaffirmed in 2010 and stabilized in 2015. This standard specifies requirements for the termination, within audio equipment, of the shields of cables supporting interconnections with other equipment, taking into account measures commonly necessary for the preservation of EMC (electromagnetic compatibility) at both audio and radio frequencies. The shielding (or screening) of audio equipment, cables, and microphones can be critical for EMC. The improper connection of these shields can cause common-impedance coupling in equipment.

Somewhat related standard is CENELEC – EN 61938: MULTIMEDIA SYSTEMS – GUIDE TO THE RECOMMENDED CHARACTERISTICS OF ANALOGUE INTERFACES TO ACHIEVE INTEROPERABILITY. EN61938 is an International Standard that gives guidance on current practice for the characteristics of multimedia analogue interfaces to achieve interoperability between equipment from different manufacturers. For more details check EN61938 standard index overview.

IEC 60958 is standard for the interconnection of digital signals. The AES3 standard parallels part 4 of the international standard IEC 60958. An AES3 signal can carry two channels of PCM audio over several transmission media including balanced lines, unbalanced lines, and optical fiber. AES3 has been incorporated into the International Electrotechnical Commission‘s standard IEC 60958, and is available in a consumer-grade variant known as S/PDIF.

Read also Shields, grounds and microphone cables (pdf) document that describes the complexities of shielding and balanced cabling explained by one of the acknowledged masters of the subject Bill Whitlock.