Can phantom power damage equipment that does not need it?

Jeremiah

Not sure where the best place is to post this...

Some mixers only have the option to turn phantom power on or off globally rather than on individual channels.

Can sending phantom power to gear that already has its own power supply damage it? I'm not thinking so much of microphones, but of things like amp-simulated DI boxes or preamps that have balanced XLR outputs.

octatonic

Yes, it can, but only under certain conditions. For example, you have phantom power turned on and use a microphone patch bay and connect up a sensitive ribbon mic and then patch it into that mixers channel. That can damage the mic, although it isn't common. I've never seen any damage to line level gear, the extra current will likely be dissipated as heat.

ecc83

Anything that is designed to plug into an XLR mic input "should" be designed to cope with phantom power. The problem arises where gear might be adapted to XLR for some reason or, rare these days, a line input on a mixer/preamp retains spook juice because of poor, lazy design.

Most equipment is (or again "should") be protected, input and output against voltages up to the internal supply rails but 48V is way above that in almost all cases so the moral is. If it is not equipped to go directly into an XLR mic input DON'T DO IT!

People are often very concerned about the damage potential of phantom power, unnecessarily so IMHO in most cases. Even the ribbon mic scenario is much more apocryphal than real but then if I had a £2000 vintage ribbon I would be very careful! Maybe buy/build a dedicated pre amp? The biggest problem is possible danger to speakers or cans from "hot plugging" ears are not fond either.

Yes, global spook juice is a bit of a PITA but a capacitor isolator box is beer into water to make if you are really bovvered!

Dave.

Danny1969

It won't cause a problem with anything that's been designed properly for balanced audio, as either / or there will be transformer coupling which blocks the DC volts of the phantom or there will be capacitor coupling which does the same. Plus the voltage is imposed on pin 2 and pin 3 so any balanced differential circuit will reject it as common mode noise 

The main thing is always remember to switch off the phantom power before you plug in or change any leads ... because in certain case using jacks rather than XLR's you can make one contact before another and that can cause problems. Also don't use any cables which aren't balanced, some very cheap mic cables have the normal 3 pin XLR connectors but are wired with 2 core wire in an unbalanced format. 

Using the ground lift switch on a DI box will disable the phantom power as the circuits between 2&3 to ground

mike257

Seen plenty of mobile phones, tablets, laptops with fried headphone outputs after being hooked up with 3.5mm jack to xlr cables and having phantom applied. Some devices will withstand it, my old Macbook would emit horrible noise but be fine afterwards, some just get nuked. Wouldn't chance it!