What's the deal with phantom power and patchbays?

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
there shouldn't be.

studio have patch panels that use tie lines to every live room. these work just like patchbays.

just make sure that the points on which you will have the Mic Pre I/Ps (the one s suppying the Phantom Power) are not normalled ("hard wired") to any other equipment. usually if they are normalled to something, it will be to Tie lines that go off to the various live rooms.

hope that helps
 
NO there should not be.
In most studios the top patch row is the output of the recording room and the bottom input into the mic pre on the console. This is usually a full normal so by patching into the mic pre out from the recording room will break the normal or by patching intothe pre on the console will break the normal. then patch the outs of the external pre just about where ever you need. I usually bring a couple of external pres to session. As well as I usually go from the pre into line in on a channel so that I can still comp and EQ from the console b4 tape/pro tools if I wish..
 
One problem...Crack and Thump in the monitors if you hot patch phantom power. Sure, you can say to yourself that you'll remember to keep the monitor volume low, and will turn phantom off while patching your mic lines, but it will happen, and the results can be nasty on your monitors.

The TRS connectors of most patch bays (either bantam, long frame or 1/4") will short the phantom during the connection process. Ideally, you should have a seperate patch bay for your mic lines and mic preamp inputs. Use XLR's for this bay, and then you can be worry free, and still have the convenience of a patch bay.

You can buy special TT jacks that switch the ground connections, making hot patching phantom easier, but I think an XLR bay is really ideal.

Cheers,

Kris
 
So the thump is the concern with phantom power and patchbays, if that's it then i'm set, because I ALWAYS turn stuff off before patching.

Yes, even after a few beers, and a few too many, and the next day...

Also, i was thinking of building myself an xlr patchbay anyway, so now i'm sold.
 
I run phantom through my bays. If its bad for gear, its not showing up yet beyond the normal wear and tear. Perhaps I'll regret it someday, but the convenience for me is worth it.

I think the main issue people have or at least one commonly talked about is that if you have a TT bay and patch with phantom on, the hot leg is getting the 48v before the cold leg, even if you patch real fast. With an XLR patch, all the pins in theory will hit the power at the same time. Again, I think this is more of something to theorize on which probably is bad but in practicality probably isnt what some folks make it out to be. If you dont patch with your phantom on in the first place, its %100 not an issue, but sometimes you do forget...

dave
 
I'm not really sure how this is possible but I've got some TT bays at work. I do foh sound and there's a transformer split before anything ever comes to me that goes to the tape side of things. If I repatch on my end w/ phantom power running it actually pops/ thumps on the tape side of things. Me not so smarty but shouldn't the transformer isolate the tape side and keep this from happening or do the install guys sell the church a snake oil job when they did the original install?
 
It makes perfect sense that the "thump" is being passed through the transformers to the recording desk. Remember, transformers pass a change in current--that's how they do their job in the first place.

Hot-patching a phantom-powered line causes an instantaneous change in the voltage across the splitter transformer primary, which causes a current to flow through the primary, and this is coupled magnetically to the secondary. In this instance, this only happens for a split second while there's a voltage difference between the two "legs" of the primary. With audio, the voltage difference is constantly fluctuating and the primary current is flowing back and forth several times per second.

I work in a TV studio and we run everything through patchbays, including mic lines. But we avoid hot-patching these as much as possible. I've instructed our board operators to cut phantom before patching mics.
 
Back
Top