![]() ![]() In that kind of equipment, if the XLR shell is linked to pin‑1, the equipment’s chassis ground will also be connected to the audio reference ground, creating a ground loop within the device itself, with all the familiar hums and buzzes. The inevitable result with this arrangement is that any noise currents carried on the cable screen are injected straight into the audio reference ground, and thus get into the audio electronics and become audible. In a perfect world that all works well but, unfortunately, it was common practice in much legacy equipment to connect pin‑1 directly to the input/output channel’s audio reference ground. I always avoid linking XLR cables together if I possibly can. However, as the shell can become dirty and corroded this connection might not be perfect, so the argument is that linking pin‑1 to the shell inside the connector itself provides more reliable grounding to maintain the Faraday Shield around the wires where they solder to the plug terminals outside of the cable screen. Thinking about the metal shell of the XLR plug for a moment, when an XLR is plugged in it’s shell also connects to the chassis via a spring contact in the socket. With balanced connections between these devices, their own local audio reference grounds are not directly connected together, so no audible ground‑loop noises can occur. To reach this Utopia, modern equipment should be built such that, inside the case, the XLR socket pin‑1 connections go straight to the chassis and nowhere else. In that way, all of the cabling and sensitive electronics are always enclosed within this Faraday Shield. When an XLR cable is plugged into the device, that Faraday Shield extends out along the cable’s screen to whatever is connected at the other end of the cable, a microphone’s outer body or the case of another device, for example. SOS Technical Editor Hugh Robjohns replies: The AES specifications do say that you should wire each pin‑1 to the shell, and there’s good sense behind that policy, but only if all of the equipment being connected together is built and wired correctly too.Ī small capacitor wired between XLR pin‑1 and the shell maintains effective screening against RF interference, while blocking low‑frequency ground currents.The idea is that the case around each piece of equipment forms a Faraday Shield to keep any environmental RF (radio‑frequency) interference out of the sensitive electronics within. Should I wire each pin‑1 to the XLR shell? I never have for any cable I’ve wired up to now, but that doesn’t mean I’ve been doing it right! What do you advise? I’m doing an installation in a chapel, using a Van Damme Starquad multicore running along the roof void.
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