[sanaka]

This is kinda OT but with the interest in interconnects around here I'm confident some of you will know exactly what my problem is

I have an Audio Technica AT822 stereo mic. It outputs unbalanced L/R on pins 2 & 3 of a standard XLR, pin 1 is ground. I built a cable to split this to two separate XLR's for standard unbalanced input to two channels of my mixing board. The signal routing all came out right, but there's a moderate hum which gets kinda bad when I touch the XLR connector at the mic end. With the mic unplugged from the cable, it turns to a radical loud buzz.

I made a couple other special XLR (unbalanced) cables for my mics and always tied the braided shield together with the signal ground. This time, noticing the fourth little solder tab on the XLR's, I kept the braid separate from signal ground and soldered it to those tabs on the connector shells figuring "chassis ground." Is this my problem?

I hope so because it would be easy to fix, either by tying the braid to signal G as before, or ?? A better way perhaps?

BTW the mixer has a two prong power plug, so it seems "chassis ground" might go nowhere.

I'm hoping to have it worked out today so I can use the mic for recording tonight and tomorrow. Thanks!!!!

Peace,
Sanaka

 

[Dreamslacker]

Tie the braid to ground. Tying it to the tab on the XLR works if tghe XLR actually plugs into a device that grounds the tab. ie. Mixer, amp etc.. The mic isn't one of them.

 

[sanaka]

Quote:

The mic isn't one of them...

Well, yeah, hence the idea of making it one of them by attaching the braid. Is the problem that my mixer has no true ground?

Anyone else?

Thanks!

Peace,
Sanaka

 

[Edwood]

Do you have to solder the shield to both ends(connectors) of the ground?

-Ed

 

[sanaka]

My initial post was perhaps scant on info. In my understanding, in an unbalanced microphone connection, two of an XLR connector's 3 pins are ground or 'return.' In addition to the three pins however, there is another solder point which contacts the shell of the connector. I soldered the cable's shield braid to these points at both ends of the cable. It seemed a likely path for RF sheilding: Mic body > XLR shell > shield braid > XLR shell > mixer chassis. But I'm getting the aforementioned hum/buzz. I see various things I can try in terms of remedy, but am hoping someone can nail the theory of it so I can have a true grasp of what's happening. Thanks!

Peace,
Sanaka