Cable Asylum Interconnects, speaker wire, power cords. Ask the Cable Guys.

---

[ Follow Ups ] Thread: [ Display  All  Email ] [ Cable Asylum ]

---

[ Alert Moderator ]

---

XLRs Possibly Miswired

Posted by Todd Krieger (A) on January 7, 2002 at 15:19:15

In Reply to: Shield/conductor interaction & dialectric choices questions posted by Cousin_Dupree on January 7, 2002 at 09:05:33:

Dimmers shoot out bursts of ghastly amounts of RFI at 120 Hz intervals. And in close proximity, this interference permeates just about everything, including shields on cables. (Unless the shield is Mu-metal.)

Balanced cables are normally *immune* to this kind of interference. In the form of "common mode" rejection. (The interference is picked up by *both* lines, but since the signal on the two lines are in opposite phase, any common mode noise products cancel each other out.) The presence of noise on a balanced line suggests the *possibility* of the XLR connectors not being wired correctly.

Miswiring XLR connectors is a *very* common mistake with DIY- If one wires the balanced cable intuitively, based on the physical XLR pin layout (the middle pin of the symmetrical layout would erroneously suggest that pin 3 should be the ground), it's probably wrong... And if it's wrong, you will not get the benefit of common-mode rejection. (I personally learned this the hard way. And I'm pretty sure others have too.)

I've also seen the XLR connectors on a balanced cable not wired in a mirror-image at each end (viewed from the solder side), which is also a common mistake. As well as mistaking pin 1 for pin 2.

Pin 1 is the ground, pin 2 is the positive signal, and pin 3 is the negative signal. (Pins 2 and 3 may be inverted.) At first glance, this wiring layout will seem strange. You may want to check this before trying extra shielding.

XLR connectors can be very tricky- even experienced DIY'ers (including myself) miswire these things from time to time. I've also come across production cables with miswired XLRs.

Whether or not this is the cause of your noise, good luck.

This post is made possible by the generous support of people like you and our sponsors:

Kimber Kable

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]

---

[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]

---