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Author Topic: Dirty phantom power  (Read 837 times)

Helge Dr. Bentsen

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Dirty phantom power
« on: November 23, 2017, 12:59:59 pm »

Someone told me today that one major difference between various digital mixing consoles is the quality of phantom power. The argument was that some desks had dirty phantom power resulting in more noise and lower quality sound in the higher frequencies on powered sources.

I've never heard about this in the past.
Is there such a thing as dirty phantom power?
Is there a reasonable explanation for why this is/is not an issue?
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Keith Broughton

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Re: Dirty phantom power
« Reply #1 on: November 23, 2017, 01:34:22 pm »

Someone told me today that one major difference between various digital mixing consoles is the quality of phantom power. The argument was that some desks had dirty phantom power resulting in more noise and lower quality sound in the higher frequencies on powered sources.

I've never heard about this in the past.
Is there such a thing as dirty phantom power?
Is there a reasonable explanation for why this is/is not an issue?
I am at a loss as to explain why someone would come up with "dirty phantom power"
It's nothing special. Just 48Vdc from the power supply.
Possibly, there might be a bad capacitor or some other defect in a specific console power supply but I have never heard of , or experienced, any "bad" phantom power.
Anyone else?
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Luke Geis

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Re: Dirty phantom power
« Reply #2 on: November 23, 2017, 01:56:14 pm »

The phantom power is part of the analog side of the A/D converter. Considering the price point in which 90% of digital mixers will fall in and the relatively high quality of modern A/D - D/A converters, there is a high probability that they will be of good quality and not be of detriment to the consoles design. I have never heard of or experienced " dirty " phantom power. I have had cables that made using phantom power a problem, but swap the cable and all is good. I have had mics go bad that wouldn't work right no matter what powered them.

Phantom power is as old as mixer technology is and the circuit design is pretty much perfected at this point in time. The likelihood that there is a bad circuit design in any modern mixer would be a far fetch. it is not a particularly difficult circuit any way. Now that does not mean that the circuit is infallible and not subject to failure. I am sure that there are more than a few mixers that have had a part within the phantom power circuit fail and cause issues. I would say that under normal operation, there is no inherently bad phantom power supplies in any modern mixer.
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John Roberts {JR}

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Re: Dirty phantom power
« Reply #3 on: November 23, 2017, 01:58:36 pm »

Someone told me today that one major difference between various digital mixing consoles is the quality of phantom power. The argument was that some desks had dirty phantom power resulting in more noise and lower quality sound in the higher frequencies on powered sources.

I've never heard about this in the past.
Is there such a thing as dirty phantom power?
Is there a reasonable explanation for why this is/is not an issue?
Maybe find somebody else to listen to.  ;D

Some people make a living inventing differences when none exists.  ::)

There is nothing about a digital mixer that suggests phantom power would be any different.

JR
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Keith Broughton

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Re: Dirty phantom power
« Reply #4 on: November 23, 2017, 02:18:35 pm »

Maybe find somebody else to listen to.  ;D

Some people make a living inventing differences when none exists.  ::)

There is nothing about a digital mixer that suggests phantom power would be any different.

JR
Maybe the phantom power needs an external clock! ;D ;D
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Ivan Beaver

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Re: Dirty phantom power
« Reply #5 on: November 23, 2017, 02:53:49 pm »

Maybe the phantom power needs an external clock! ;D ;D
Or a "hum eliminator"  YEAH-that will get rid of the noise-and the signal---------
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Jeff Bankston

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Re: Dirty phantom power
« Reply #6 on: November 23, 2017, 03:44:32 pm »

Or a "hum eliminator"  YEAH-that will get rid of the noise-and the signal---------
hhhmmmmmmmmmmmm ! now you got me thinkin !

http://www.youtube.com/watch?v=SKRma7PDW10
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Art Welter

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Re: Dirty phantom power
« Reply #7 on: November 23, 2017, 03:49:15 pm »

I am at a loss as to explain why someone would come up with "dirty phantom power"
It's nothing special. Just 48Vdc from the power supply.
Possibly, there might be a bad capacitor or some other defect in a specific console power supply but I have never heard of , or experienced, any "bad" phantom power.
Anyone else?
I owned a very cheap Behringer 4 mic pre analog mixer that had "normal" noise and distortion levels with dynamic microphones, but had a peculiar "whining" noise using the phantom power with condenser mics. The phantom power was a global switch, it did not cause noise in the dynamic mics, but the noise varied between different types of condenser microphones, the "true condensers" were different than the back electrets.  Using the same mics and cords, the noise was absent using other mixers, or a little two channel phantom power supply, (which cost as much as the mixer..).

Considering the cost of the mixer, and how it generally was not used with condenser mics, I never pursued the cause of the problem, but it definitely provided "bad" phantom power. A quick check would not reveal the problem- if you were listening in a noisy room you would not notice the weird noise. This mixer was from the late 1990's before Behringer was doing most of their own manufacturing, I suspect it's "wall wart" power supply may have been re-supplied and varied in some way from the original design specification.

Never have experienced "bad phantom" power on any other mixers, but once was enough to know it is possible, even if I don't know exactly what caused it.

Art
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John Fruits

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Re: Dirty phantom power
« Reply #8 on: November 23, 2017, 04:01:55 pm »

Since I am a silly old git in forum land I have 1 question.
Don't you just hate it when a superhero goes bad?
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John Roberts {JR}

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Re: Dirty phantom power
« Reply #9 on: November 23, 2017, 04:29:38 pm »



Never have experienced "bad phantom" power on any other mixers, but once was enough to know it is possible, even if I don't know exactly what caused it.

Art
That does not remotely support the thesis that some digital mixers have dirty phantom power. Only that old cheap small Behringer mixers could (did once).

FWIW there are multiple factors that influence the likelihood of phantom power related noise...

Since competent preamp designs reject common mode noise it isn't linear with the actual 48V noise. Further a squirrely mic (or cable) could imbalance the input impedances degrading CM rejection of even a well designed preamp.

JR

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