View Full Version : Phantom Power Blocker??

05-03-2006, 07:54 PM
Pro audio question here:

are there any devices that will block phantom power?

I am most likely going to purchase the Digitech GNX3000 guitar gizmo. One of its uses will be to interface my electric guitar with the church PA.

The church PA has phantom power enabled for all channels - it is all or none and we do use it.

The gnx3000 has xlr outs AND 1/4" outs. I was going to run the xlr to the pa, run the 1/4 " to a monitor amp. The gnx3000 owners manual recommend no phantom power. I emailed Digitech and they said that protection circuitry is built in, but there is a slim chance of damage and that is the reason for the warning.

Any ideas?

05-03-2006, 09:01 PM
call Rapco and see if this will do it. I suspect it will.


05-03-2006, 09:46 PM
THAT'S why I love this forum ! At the present I have absolutely no use for this bit of information, but someday that little nugget will most likely be useful. Lots to learn on this site if you open your mind to what is said. :up:

05-03-2006, 09:53 PM
It should also be good for keeping your ES free from phantom power.

05-03-2006, 10:07 PM

I'll give them a call tomorrow, and will post what I find out...

05-04-2006, 06:10 PM
I called the folks at Rapco today and they said that device would indeed block phantom power.

The last thing I'm checking out is this:

The IsoBlox impedance is 600 Ohms, and the XLR output impedance on the GNX3000 is 120 Ohms. I emailed Digitech and they said this should not cause any problems.

What do you guys think?

I'm thinking it will probably be OK. I had an impedance mismatch with the Baggs DI and the KK Pure Western on the Lowdeo and Avalons I had, and didn't have any problems.

05-04-2006, 09:05 PM
You will be fine.

05-04-2006, 11:30 PM
This is way over my head.

Rick Turner
05-05-2006, 12:32 AM
Ah yes, really cheap. And really ineffective...that's just what we need more of...

You need capacitive isolation OR a transformer. Don't worry about exact impedance match, in fact what you really want is a match of about 1:10 in output to input in order for the input impedance not to load down the output impedance of the source and try to pull current down the line.