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Author Topic: 48v protocol  (Read 749 times)

Richard Oppenheimer

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48v protocol
« on: March 01, 2024, 04:05:07 PM »

What is the best practice for safely using phantom power on condenser mics? Should I turn phantom off for each channel before I unplug the xlrs? Is it a bad thing to unplug a mic from a muted channel that still has the 48v on?
I know to mute all channels before turning 48v on or off, but what are the rules when connecting /disconnecting the cable from the actual microphones?

Thanks
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John Roberts {JR}

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Re: 48v protocol
« Reply #1 on: March 01, 2024, 04:38:18 PM »

What is the best practice for safely using phantom power on condenser mics? Should I turn phantom off for each channel before I unplug the xlrs? Is it a bad thing to unplug a mic from a muted channel that still has the 48v on?
I know to mute all channels before turning 48v on or off, but what are the rules when connecting /disconnecting the cable from the actual microphones?

Thanks
I am not aware of any protocol per se, but take care to not accidentally short either pin 2 or pin 3 to ground as this can drive -48V into mic preamp inputs (through the DC blocking capacitors).

This is a known concern working with studio patch bays, not so much for live SR.

JR
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Brian Jojade

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Re: 48v protocol
« Reply #2 on: March 01, 2024, 06:06:09 PM »

There were a few reports a while back on a certain model of mixer that could fry inputs if devices were connected/disconnected while phantom power was turned on.

I personally haven't experienced any issues though and often forget that I have phantom power on sometimes.  I find it handy on the X32 that there's at least a red LED that lights up next to the connector reminding me phantom is on.  While most things don't care about phantom, certain things do, so caution is warranted.
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Chris Hindle

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Re: 48v protocol
« Reply #3 on: March 01, 2024, 08:39:57 PM »

What is the best practice for safely using phantom power on condenser mics? Should I turn phantom off for each channel before I unplug the xlrs? Is it a bad thing to unplug a mic from a muted channel that still has the 48v on?
I know to mute all channels before turning 48v on or off, but what are the rules when connecting /disconnecting the cable from the actual microphones?

Thanks
I leave the channel off until the mic is fully connected, and kill the strip before it is unplugged.  A lot of mic's make a nasty pop when power is applied or removed. Generally i set up the board (rough gain, phantom, etc) before I wire the stage, with all channels muted.
Chris.
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Robert Lunceford

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Re: 48v protocol
« Reply #4 on: March 02, 2024, 02:20:05 AM »

There were a few reports a while back on a certain model of mixer that could fry inputs if devices were connected/disconnected while phantom power was turned

I remember that too. I believe it was the Soundcraft digital boards that had that issue.
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Chris Grimshaw

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Re: 48v protocol
« Reply #5 on: March 02, 2024, 05:30:40 AM »

I remember that too. I believe it was the Soundcraft digital boards that had that issue.

Yeah, I heard similar. Had a guy bring a UI24 through my usual venue, to mix band's IEMs via analogue split. He said it was vitally important to make sure he'd switched phantom before connecting/disconnecting XLRs, or the preamp might be damaged.

I mean, even my crappy old Behringer analogue desk doesn't care, so I was a little dismayed that something much more expensive and modern might be so sensitive.

FWIW, I just make sure all the inputs (except BGM, if it still needs to be running) are muted before I start unplugging things.

Chris
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Mike Caldwell

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Re: 48v protocol
« Reply #6 on: March 02, 2024, 06:55:28 AM »

I think there was a Digico stage box input card that did not like getting a mic connected with the phantom power turned on.

John Roberts {JR}

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Re: 48v protocol
« Reply #7 on: March 02, 2024, 11:22:40 AM »

For a little historical perspective, back in the early days of wireless microphones the external receivers would plug into console mic inputs. Many of the first generation wireless receiver designs were not robust and protected against exposure to phantom voltage on their outputs.

The design engineers figured it out after suffering too many field failures in early production runs.


JR
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ProSoundWeb Community

Re: 48v protocol
« Reply #7 on: March 02, 2024, 11:22:40 AM »


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