Phantom power???

Wayne8 · #1 10-15-2008, 09:44 PM

I have a question about phantom power. Two guitarists and a bassist in my church run through pedals and DI into the church's board. We've started having problems, one dead DI, a POD experiencing strange distortion, etc... There's a 15 year old running the board and I know the board has phantom power, though I don't really know how it works. I was wondering, if phantom power is turned on to a channel that the guitars are in, could damage to the pedals result?

Thanks.

bongomania · #2 10-15-2008, 09:57 PM

Yes, that is possible. Not all DI's (or other balanced outputs) are protected against incoming voltage, and it does happen that gear gets wrecked that way sometimes. You have to either make sure the balanced power is switched off for the channels you plug into, or buy gear that is designed to withstand incoming voltage. Regrettably that's not something you can assume, even with good/pro gear.

mrokern · #3 10-15-2008, 11:29 PM

Quote:

Originally Posted by bongomania

Yes, that is possible. Not all DI's (or other balanced outputs) are protected against incoming voltage, and it does happen that gear gets wrecked that way sometimes. You have to either make sure the balanced power is switched off for the channels you plug into, or buy gear that is designed to withstand incoming voltage. Regrettably that's not something you can assume, even with good/pro gear.

Precisely why I try to use either a trusted DI, or if I do come off my amp, an iso box (basically an in-line isolation transformer that won't pass phantom power).

-Mark

Wayne8 · #4 10-16-2008, 08:17 PM

Well, I've got the phantom power switched off for now. There's an on/off button for it on the back (it's a 24 channel Mackie). We're going to have to go online and find the manual for that board to see how you turn phantom power on/off for particular channels, it wasn't obvious just looking at it. But since I know no one uses it anyway, I've got it switched off in back. I don't know if the one pedal was damaged or died a natural death, the guy who owns it doesn't take real good care of it. The distortion on the POD turned out to be a bad cable connection.

Thanks.

mrokern · #5 10-16-2008, 10:02 PM

Quote:

Originally Posted by Wayne8

Well, I've got the phantom power switched off for now. There's an on/off button for it on the back (it's a 24 channel Mackie). We're going to have to go online and find the manual for that board to see how you turn phantom power on/off for particular channels, it wasn't obvious just looking at it. But since I know no one uses it anyway, I've got it switched off in back. I don't know if the one pedal was damaged or died a natural death, the guy who owns it doesn't take real good care of it. The distortion on the POD turned out to be a bad cable connection.

Thanks.

You can't turn it on and off individually...if it's the model I'm thinking it is, the phantom is global.

-Mark

Wayne8 · #6 10-17-2008, 07:50 AM

OK. Thanks!

vinny · #7 10-17-2008, 08:25 AM

Quote:

Originally Posted by mrokern

You can't turn it on and off individually...if it's the model I'm thinking it is, the phantom is global.

-Mark

Yup, on that board it's all or nuthin'

dcr · #8 10-17-2008, 04:39 PM

Quote:

Originally Posted by mrokern

You can't turn it on and off individually...if it's the model I'm thinking it is, the phantom is global.

-Mark

Actually, I think you can..sorta. Normally it's global, but you can set it up for specific phantom channels, IIRC. Requires mod to the internals of the Mackie. And I think it breaks into groups of four. I've never done my 24-4 that way, because I have individual tube mic pre's to run my phantoms as needed. Plus it makes 'em sound super-fat!

And yep, it is certainly a possibility to damage certain equipment using the direct outs from stuff if phantom is on. I believe I diddled a keyboard player's Behringer amp DI that way a few months ago on a sound gig. Lotsa "help" setting up for a "Battle Of The Bands" competition.

dcr

TimmyP · #9 10-18-2008, 07:42 PM

Any DI should protect the attached instrument from phantom power (I've yet to see one that did not, unless it was broken).

Some units that have DI outs (PODs, wireless mic receivers, amp heads) do not react well to the presence of phantom power (and some of these units ain't cheapies). This should be considered a design flaw, but ya gotta make it work - either turn off the phantom, or use the unit's 1/4" out through a DI or an isolation transformer (whichever is the more appropriate).

bongomania · #10 10-18-2008, 07:45 PM

Sorry man, but that's just wrong. There are lots and lots of DI outputs out there which lack protection from phantom power, and that includes a lot of high-end gear. Not all DI's include an output transformer.

TimmyP · #11 10-18-2008, 07:50 PM

Quote:

Originally Posted by bongomania

Sorry man, but that's just wrong. There are lots and lots of DI outputs out there which lack protection from phantom power, and that includes a lot of high-end gear. Not all DI's include an output transformer.

A DI is either a transformer, or an active circuit. I've never seen either one pass DC on to the input of the DI. If one does, it is broken.

bongomania · #12 10-18-2008, 07:55 PM

But (a) there is nothing inherent to the phrase "active circuit" that implies protection from DC, and (b) there are countless examples of gear being damaged in exactly this manner. Typically the gear damaged is an amp, preamp, or electronic keyboard. Maybe you haven't ever seen it, but I have, and I've seen lots of threads about it in the amps forum as well.

TimmyP · #13 10-18-2008, 08:02 PM

Quote:

Originally Posted by bongomania

But (a) there is nothing inherent to the phrase "active circuit" that implies protection from DC, and (b) there are countless examples of gear being damaged in exactly this manner. Typically the gear damaged is an amp, preamp, or electronic keyboard. Maybe you haven't ever seen it, but I have, and I've seen lots of threads about it in the amps forum as well.

Yes, a lot of gear can be damaged by phantom power. But I've never seen a standalone DI that allowed a connected (via the 1/4") piece of gear to be damaged by the phantom power that's going into the DI.