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Author Topic: Y-ing a signal into a mixer with Phantom power already on it.  (Read 5074 times)

Kevin Maxwell

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Y-ing a signal into a mixer with Phantom power already on it.

This is for a SMAART rig. I have just changed the way I inject pink noise into the mixer. I now have a noise plug (pink noise in an XLR) it needs Phantom power. I also need Phantom power for the measurement mics, the USB preamp audio interface has global Phantom power. I want to use an XLR Y cord to route the pink noise into one channel of the USB preamp and one channel of the console. This means that I will be putting Phantom power into the mixer from the USB preamp. Is this a no no? I was also thinking of making a Y cable with a female XLR to one male XLR and one TRS ¼” connector for when I want to go into a ¼” input instead of an XLR input. This also brings up the question of injecting 48v into the mixer into the ¼” input. I just used this for the first time the other day and I had a Whirlwind Line Balancer/Splitter handy. So first I tested to see if it was linear and it was, so I used that between the noise plug and the mixer just to be safe.     
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Mac Kerr

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Re: Y-ing a signal into a mixer with Phantom power already on it.
« Reply #1 on: January 22, 2016, 12:01:40 pm »

Y-ing a signal into a mixer with Phantom power already on it.

This is for a SMAART rig. I have just changed the way I inject pink noise into the mixer. I now have a noise plug (pink noise in an XLR) it needs Phantom power. I also need Phantom power for the measurement mics, the USB preamp audio interface has global Phantom power. I want to use an XLR Y cord to route the pink noise into one channel of the USB preamp and one channel of the console. This means that I will be putting Phantom power into the mixer from the USB preamp. Is this a no no? I was also thinking of making a Y cable with a female XLR to one male XLR and one TRS ¼” connector for when I want to go into a ¼” input instead of an XLR input. This also brings up the question of injecting 48v into the mixer into the ¼” input. I just used this for the first time the other day and I had a Whirlwind Line Balancer/Splitter handy. So first I tested to see if it was linear and it was, so I used that between the noise plug and the mixer just to be safe.   

Why not just use the noise generator built into Smaart? You don't need the stick, just take one out of your interface to the console, and one can either loop back into an input for the reference input, or that can be done internally.

Mac
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Kevin Maxwell

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Re: Y-ing a signal into a mixer with Phantom power already on it.
« Reply #2 on: January 22, 2016, 02:19:01 pm »

Why not just use the noise generator built into Smaart? You don't need the stick, just take one out of your interface to the console, and one can either loop back into an input for the reference input, or that can be done internally.

Mac

Sometimes I am working on someone’s system that the mixer doesn’t have a built in Pink noise generator. Or I don’t have the time to try to figure out how to make it work the way I want. So I have standardized on supplying the pink noise from outside the console.
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Tim McCulloch

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Re: Y-ing a signal into a mixer with Phantom power already on it.
« Reply #3 on: January 22, 2016, 02:46:28 pm »

Sometimes I am working on someone’s system that the mixer doesn’t have a built in Pink noise generator. Or I don’t have the time to try to figure out how to make it work the way I want. So I have standardized on supplying the pink noise from outside the console.

Mac is referring to the noise generator built into SMAART, not the console.  You might want to re-read his reply.

That said, I put a 10 minute WAV file of pink noise (edited from Bink's Audio Test CD) on my audio player for when I just need some pink noise and not using Smaart.
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Kevin Maxwell

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Re: Y-ing a signal into a mixer with Phantom power already on it.
« Reply #4 on: January 22, 2016, 03:52:27 pm »

Mac is referring to the noise generator built into SMAART, not the console.  You might want to re-read his reply.

That said, I put a 10 minute WAV file of pink noise (edited from Bink's Audio Test CD) on my audio player for when I just need some pink noise and not using Smaart.

WOW my reading comprehension is sorely lacking today. I keep going to bed late and waking up early because of a few things in the works on my mind. So I am a bit sleep depraved and yes I did mean to say depraved and not deprived. 

I don’t know if it is still the case but there was a problem of getting accurate times with the internal pink noise and the impulse measurements and I use that capabilities a lot to set delay speaker times. So I never got into using the internal generator.
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Mac Kerr

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Re: Y-ing a signal into a mixer with Phantom power already on it.
« Reply #5 on: January 22, 2016, 04:35:08 pm »

WOW my reading comprehension is sorely lacking today. I keep going to bed late and waking up early because of a few things in the works on my mind. So I am a bit sleep depraved and yes I did mean to say depraved and not deprived. 

I don’t know if it is still the case but there was a problem of getting accurate times with the internal pink noise and the impulse measurements and I use that capabilities a lot to set delay speaker times. So I never got into using the internal generator.

There was an issue with the absolute time displayed, but since you are always only interested in the time difference between two signals the offset error cancels out. This was only when using the internal signal path. It was never an issue coming out of your interface and back in for reference.

Mac
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Kevin Maxwell

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Re: Y-ing a signal into a mixer with Phantom power already on it.
« Reply #6 on: January 22, 2016, 05:57:48 pm »

There was an issue with the absolute time displayed, but since you are always only interested in the time difference between two signals the offset error cancels out. This was only when using the internal signal path. It was never an issue coming out of your interface and back in for reference.

Mac

Thank you for the help on that way of doing it I will have to play with it again, it didn’t work properly that last time I tried it but I had a different USP preamp back then.

But can anyone answer my original question about Phantom power any Y-ing?
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David Sturzenbecher

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Re: Y-ing a signal into a mixer with Phantom power already on it.
« Reply #7 on: January 22, 2016, 11:25:55 pm »

Thank you for the help on that way of doing it I will have to play with it again, it didn’t work properly that last time I tried it but I had a different USP preamp back then.

But can anyone answer my original question about Phantom power any Y-ing?

This is the exact same setup as a monitor console applying phantom power to a passive split, and the FOH console is seeing the 48V.   It happens 1000's of times a day, and is perfectly fine. XLR inputs are all generally fine with having phantom applied by an external source, but the same cannot be said about 1/4" inputs.
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Kevin Maxwell

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Re: Y-ing a signal into a mixer with Phantom power already on it.
« Reply #8 on: January 22, 2016, 11:41:03 pm »

This is the exact same setup as a monitor console applying phantom power to a passive split, and the FOH console is seeing the 48V.   It happens 1000's of times a day, and is perfectly fine. XLR inputs are all generally fine with having phantom applied by an external source, but the same cannot be said about 1/4" inputs.

I always had transformer isolated splits, even 3 ways when there was also a broadcast split. One went direct and the other two were transformer isolated. And even that didn’t help when you had Vari-Lites all over the stage and the cabling was almost intertwined. Sorry flashing back to shows past. 

I believe you and it makes a lot of sense. I was thinking of the times when I had to feed a console out to something that had phantom on it. I got in the habit of transformer isolating everything. I just didn’t want to mess up someone else’s console.

Thank you for the reply. And I won’t make the Y cable to ¼” version.
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Jordan Wolf

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Re: Y-ing a signal into a mixer with Phantom power already on it.
« Reply #9 on: January 23, 2016, 01:57:12 am »

Transformer isolation is your friend.


- Jordan Wolf
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Re: Y-ing a signal into a mixer with Phantom power already on it.
« Reply #9 on: January 23, 2016, 01:57:12 am »


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