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Author Topic: Phantom power issue  (Read 3317 times)

Guy Morris

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Phantom power issue
« on: July 25, 2011, 11:10:37 am »

Hello

Came across a puzzling scenario at the weekend and of course it manifested itself as the minutes ticked away to gates open. :(

I was using an M7cl on monitors via an analogue M/C up to FOH they had a Presonus studio live desk.

It was agreed that the M7 would provide phantom power so I went through the required channels dialing it in. FOH were already line checking all the mics to their end and then they got to the overheads and nothing, obviously I checked that 48v was on and assigned to everything correctly and on checking the Dis then discovered they were not powered either, we decided to switch off the M7 48v from the main set up page (checked to see if that was on in first place.. it was)and then supplied phantom from the FOH desk which powered everything straight off.

Time (as always) was tight so I had no opportunity to check this problem out  what I do know is that 1 FOH phantom was off  so no conflict issue
                 2 Stagebox has no switch for phantom select so no error there
                 3 Stagebox does have an earth lift button per channel but it did not seem to make a difference in getting any phantom via the M7 (my first suspicion of the cause)

The stagebox has Veam multi out connectors  with 1:1 transformer isolating on each channel could this block phantom power supplied via the monitor multiway or should it be available from either multipin connection?

Any suggestions?

I will be setting up the M7 and an LS9  with the same stagebox to see if I get the same issues (no time pressure this time) no doubt something obvious that under pressure I could not see but at least a simple solution was the other  desk supplied the phantom!

Thanks


« Last Edit: July 25, 2011, 11:12:44 am by Guy Morris »
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Andrew Makinson

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Re: Phantom power issue
« Reply #1 on: July 25, 2011, 11:19:48 am »

The stagebox has Veam multi out connectors  with 1:1 transformer isolating on each channel could this block phantom power supplied via the monitor multiway or should it be available from either multipin connection?

Yes.  The transformers will block phantom power.
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Andrew Makinson
Grace Covenant Church
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Mac Kerr

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Re: Phantom power issue
« Reply #2 on: July 25, 2011, 11:23:45 am »

Time (as always) was tight so I had no opportunity to check this problem out  what I do know is that 1 FOH phantom was off  so no conflict issue
                 2 Stagebox has no switch for phantom select so no error there
                 3 Stagebox does have an earth lift button per channel but it did not seem to make a difference in getting any phantom via the M7 (my first suspicion of the cause)

The stagebox has Veam multi out connectors  with 1:1 transformer isolating on each channel could this block phantom power supplied via the monitor multiway or should it be available from either multipin connection?

There should never be a "conflict" with phantom power. It is OK to power from both consoles.

If there is a pin 1 lift switch on the feed to the console providing phantom, the switch must have pin 1 connected. The phantom voltage is between pin 1, and pins 2&3. If pin 1 is lifted there is no voltage.

If there is a transformer between the console and the mics phantom will not pass. Only the console on the direct out of the splitter can supply phantom. I would make a WAG that this was your problem.

Mac
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Mark Oakley

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Re: Phantom power issue
« Reply #3 on: July 25, 2011, 04:43:29 pm »



There should never be a "conflict" with phantom power. It is OK to power from both consoles.


So just to clarify, even on a passive split (non-transformer) it's okay for both boards to supply 48v? Would this sum to 96V. or damage the mics?

-thanks, Mark
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Larry Sheehan

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Re: Phantom power issue
« Reply #4 on: July 25, 2011, 04:58:46 pm »

So just to clarify, even on a passive split (non-transformer) it's okay for both boards to supply 48v? Would this sum to 96V. or damage the mics?

-thanks, Mark

The 2 sources would be in parallel, so voltages would not be added to each other.
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Larry Sheehan - San Gabriel Sound

Mac Kerr

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Re: Phantom power issue
« Reply #5 on: July 25, 2011, 05:02:15 pm »

So just to clarify, even on a passive split (non-transformer) it's okay for both boards to supply 48v? Would this sum to 96V. or damage the mics?

Yes. The 2 power supplies are in parallel not series, and are isolated by 6.8KΩ resistors at each console.

Mac
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Guy Morris

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Re: Phantom power issue
« Reply #6 on: July 26, 2011, 08:51:29 am »

Hi Guys

Thanks for the answers,looks like it is the 1:1 transformers! great to have them there  but it caught me out as the multi outs were connected as labeled FOH and MON ,so a simple swap over of the two multis would have fixed it by putting me on the right side of the transformer split, hmm a heat of the moment mind block! and that last minute request for monitors to supply phantom as the FOH guy was struggling to get his head around the Presonus desk swerved the set up plan.

Maybe time to go digital snake... the temptation gets stronger

Thanks
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ProSoundWeb Community

Re: Phantom power issue
« Reply #6 on: July 26, 2011, 08:51:29 am »


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