Phantom power standards?

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This is about "phantom power" provided on many commercial microphone
mixers. Circuit diagrams that I have been able to find on the Internet
show the power being fed through 6800 ohm pullup resistors on the two
sides of the balanced line. Is this typical of commercial gear?
 
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"Detector195" <Detector195@yahoo.com> wrote in message
news:6213f73a.0408110412.25b3976a@posting.google.com

> This is about "phantom power" provided on many commercial microphone
> mixers. Circuit diagrams that I have been able to find on the Internet
> show the power being fed through 6800 ohm pullup resistors on the two
> sides of the balanced line. Is this typical of commercial gear?

Yes.

See for yourself:

http://www.rane.com/pdf/dms22sch.pdf

http://www.rane.com/pdf/ms1bsch.pdf
 
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"Arny Krueger" <arnyk@hotpop.com> wrote in message
news:sJadnT5asKDgk4fcRVn-iQ@comcast.com...
> "Detector195" <Detector195@yahoo.com> wrote in message
> news:6213f73a.0408110412.25b3976a@posting.google.com
>
> > This is about "phantom power" provided on many commercial microphone
> > mixers. Circuit diagrams that I have been able to find on the Internet
> > show the power being fed through 6800 ohm pullup resistors on the two
> > sides of the balanced line. Is this typical of commercial gear?
>
> Yes.
>
> See for yourself:
>
> http://www.rane.com/pdf/dms22sch.pdf
>
> http://www.rane.com/pdf/ms1bsch.pdf

From the rec.audio.pro FAQ:

"Q3.5 - What is phantom power? What is T-power?
.....
" The more common of these methods is called "phantom power" and is
covered by DIN spec 45596. The positive terminal of a power
supply is connected through resistors to both signal leads of a
balanced microphone, and the negative terminal is connected to
ground. 48 volts is the preferred value, with 6800 ohm resistors
in each leg of the circuit, but lower voltages and lower resistor
values are also used. The precise value of the resistors is not
too critical, but the two resistors must be matched within 0.4%."
......

Note that the closest value of high-precision (1% or better)
resistors tends to be 6.81K
 
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Detector195 wrote:

> This is about "phantom power" provided on many commercial microphone
> mixers. Circuit diagrams that I have been able to find on the Internet
> show the power being fed through 6800 ohm pullup resistors on the two
> sides of the balanced line. Is this typical of commercial gear?

Depends on how you define standard. Voltages vary. 48 is the tops, but
it not uncommon to have 12 or 24 volts DC. Wireless lavs frequently run
at 5 volts or so.

A center tapped input transformer can also be used to feed phantom
voltage. And some lavaliers have a separate single line for phantom.

Bob



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> Detector195 wrote:
> > This is about "phantom power" provided on many commercial
> > microphone mixers. Circuit diagrams that I have been able to
> > find on the Internet show the power being fed through 6800
> > ohm pullup resistors on the two sides of the balanced line. Is
> > this typical of commercial gear?


"Bob Urz" wrote ...
> Depends on how you define standard. Voltages vary.
> 48 is the tops, but it not uncommon to have 12 or 24
> volts DC. Wireless lavs frequently run at 5 volts or so.

The ~5 volt power supplied to wireless mics, portable
recorders (like DAT & MD), and even computer sound
cards is not "phantom power" in the strict sense of the
word. It is more generally described as "bias voltage".
 
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