Mic Splitter troubles

[Micklure]

Hello fellow ControlBoothians. I'm trying to setup a monitor mixer. I've got inputs hard wired into my stage that come to my control booth patch bay. In the patch bay, I can then patch those inputs directly into my FOH mixer, or (allegedly) into a series of Pro Co MS82 transformer/isolated rack splitters. The direct output then goes to my FOH mixer and the ISO output goes to a range of outputs on the patch bay, which can be snaked to the monitor mixer (or recording setup, or whatever else I may need.)

However, I haven't used these splitters since I started my position at this venue. We've always just done monitors from the FOH aux busses. Here's where I run into a problem: I can test each channel on the FOH mixer through the splitters with no issues. But when I connect my monitor mixer (via the patch bay) to the ISO outputs from the splitters, I lose signal to my FOH mixer, but gain signal to the monitor mixer. It happens on a channel-by-channel basis; that is, as I patch each channel out from the splitters, I lose that channel on the FOH mixer. Am I missing some blatant thing I ought to have known?

Thanks for your help, as always.

 

[Footer]

After you hit the split, you need to patch both the input on your monitor desk and the input of your FOH desk. So... input patch into splitter then splitter to FOH desk via the main out and Splitter ISO out to Monitor desk. Your patch pay is set up to not automatically normalize those splits.

 

[FMEng]

I think Kyle is on the right track. On some double row patch panels, the output jack (typically the top row) has an internal connection to the input jack (typically the bottom row). That internal connection is called a "normal." On a patch panel with full normals, the internal connection between the two jacks is broken any time something is plugged into either one. On a patch with half normals, the connection is broken only when something is plugged into the input jack.

Half normals allow a source to be patched to a second destination. Half normals are common on line level patches, but not mic patches. It's also possible to have patch panels without any normals, which would require a patch cord to make every connection. Or a patch could be a custom build with normals on some things and not others.

 

[Micklure]

Thanks for your quick replies! After Kyle's advice, I did a lot of learning about patchbay normalling; there's so much I didn't know. What you're both talking about seems to corroborate my experiences so far. When I get to work this morning, I'll re-evaluate with this new knowledge.

 

[Micklure]

Just to follow up - you were exactly right. The issue was the normalling setup of my patch bay. Many thanks!