Hum in the studio

[multree]

Heya.... so I wanted to combine two rooms into one studio and built two patch panels with 4 XLR and one TRS connector.

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I used Neutrik jacks and Cordial cables. The cables go into the dry wall, up to the ceiling and out into the second room. Inside of the ceiling to the other end of the room, into the drywall again and down to the patch panel.

there are power cables in the ceiling as well (for the light). but no audio cable is touching a power cable.

still. it hums as a hillbilly.

the hum almost goes away when a dynamic mic is attached. but if there's a ribbon mic attached or (even worse) there's nothing attached to the jack in the "live room" it hums and HUMS.....

anything obvious I might have done wrong?

[BertKoor]

Perhaps you forgot to connect shielding of the cables to the ground / chassis?

Maybe better post a photo of the inside, how all is soldered. Close-up...

[multree]

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[vurt]

does it go if lights are out?
are they strip lights?

[multree]

now that you mention it it looks like I soldered the damn thing the wrong way around.... haven't I ?

[vurt]

that would probably do it

[multree]

thanks for asking for pictures..... looks like I'm a special kind of stupid....

[BertKoor]

Next to the red wires I see unused soldering connections for the metal chassis itself. If you're redoing it anyway, that should be connected to the shield of the wire: xlr pin 1. Usually there are numbers moulded next to the connector pins. 1 -> 1, 2-> 2, 3-> 3.

[multree]

Hi Bert,

thanks again..... just switched the wires and also soldered this connection to pin 1, and lo and behold.... it works.... now that was an easy fix.

cheers,
mully

[BertKoor]