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-   -   Plugging in phantom powered mics (https://www.dvinfo.net/forum/all-things-audio/46311-plugging-phantom-powered-mics.html)

Dave Largent June 16th, 2005 04:24 AM

Plugging in phantom powered mics
 
I've seen some instructions that come with phantom
powered mics say that you should plug them in
before applying the phantom power.
In the past, I've plugged in mics with the
power already applied and have not noticed any
problem.
Does anyone know anything about this? Do you
always wait till they're plugged in before hitting the
power?

Bob Costa June 16th, 2005 04:39 AM

I try to wait to plug ANYTHING in only when the power is off. I would guess a mic is a sensitive instrument, so I try to use that rule for mic. I admit I don't always remember. I doubt it is a binary decision, but more one of each time causing a little bit of extra wear and tear on the diaphagm until one day you wonder what happened to your microphone.

Steve House June 16th, 2005 04:43 AM

Quote:

Originally Posted by Dave Largent
I've seen some instructions that come with phantom
powered mics say that you should plug them in
before applying the phantom power.
In the past, I've plugged in mics with the
power already applied and have not noticed any
problem.
Does anyone know anything about this? Do you
always wait till they're plugged in before hitting the
power?

"Hot swapping" almost any electronics that haven't been explicitly designed for it could lead to damage. Plus, if the phatom power is on there's a good chance the mike preamps are too and it could damage the very sensitive input circuits. And if power is on to the mixer and monitors that are being fed, the voltage spike coming through when the mike is hot plugged could create an electronics and speaker damaging very high volume "bang."

Jay Massengill June 16th, 2005 07:14 AM

It's definitely better to plug and unplug any mics when phantom power is OFF and the system volume controls are down.
Even dynamic mics will cause a loud pop through the system if phantom is on and you connect or disconnect.
As was stated earlier, it usually doesn't kill anything right then, but it's needless stress on the mic, preamp circuit, mixer, amp and speakers.
Don't forget that when turning phantom off it still takes several seconds for all the power to bleed down.

Patrick King June 16th, 2005 11:39 AM

Quote:

Originally Posted by Jay Massengill
Don't forget that when turning phantom off it still takes several seconds for all the power to bleed down.

Jay, That explains alot. Now that you've said that (written it), the light has come on. I've turned of phantom power before and immediately plugged in a mic and got that pop which made me second guess if I'd really got the phantom power off. If the phantom power circuit has to discharge the residual power over a couple of seconds, that would account for me plugging in other times and not getting the telltale pop.

Thanks, you made your money today...take the rest of the day off!

Nate Ford June 16th, 2005 11:51 AM

this will probably never come up for you, but phantom power can kill ribbon mics. (it won't hurt any other non-phantom mics.) there aren't any ribbon mics you'd use in video production, but they are used in the rcording world.

Jay Massengill June 16th, 2005 12:48 PM

Ribbon mics are coming back into favor though, so running into one when shooting in a music environment could be more common than it was.

Dave Largent June 16th, 2005 02:49 PM

I wonder what would happen if you accidentally sent
48V phantom to a wireless receiver?

Jay Massengill June 17th, 2005 07:51 AM

It depends on how the connection is wired, how robust the phantom power circuit is and how robust the receiver output is. The effects range from nothing wrong happening to something burning up.
If the receiver uses a balanced connection, then usually there is no problem with something frying. Some devices don't like having phantom sent into their outputs and either their audio or metering is affected but nothing is damaged.
Some receivers use various forms of unbalanced outputs and that can cause a problem, usually shorting one leg of the phantom power to ground. That can burn up some phantom circuits. Usually there is a caution about this in the operators manual if it is susceptible.


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