Help a newbie with phantom power at DVinfo.net

Go Back   DV Info Net > Canon EOS / MXF / AVCHD / HDV / DV Camera Systems > Canon HDV and DV Camera Systems > Canon XL and GL Series DV Camcorders

Canon XL and GL Series DV Camcorders
Canon XL2 / XL1S / XL1 and GL2 / XM2 / GL1 / XM1.


Reply
 
Thread Tools Search this Thread
Old September 28th, 2005, 01:29 PM   #1
Regular Crew
 
Join Date: Mar 2005
Location: Ponca City, OK
Posts: 61
Help a newbie with phantom power

Can the XLR connections on the XL2 be used to power something other than audio devices. Like say a small lcd monitor? Noticed that most 6-7inch lcd monitors require 12 v DC and consume less than 6w. Could this be done???? Or am I a complete idiot for asking?
Andrew C. Stewart is offline   Reply With Quote
Old September 28th, 2005, 01:43 PM   #2
Regular Crew
 
Join Date: Aug 2004
Location: Eau Claire, WI
Posts: 167
Not to worry, you are not a complete idiot.

Unfortunately, however, I don't believe it can be done. If I remember correctly, phantom power is typically 48v at only a few milliamps, so it would not be able to actually power such a device as it was never intended to run more than a tiny mic capsule and preamp. At 12 volts and 6 watts the current draw would be 500ma. Your best option for the LCD is probably to use a separate battery pack.

'Hope this helps, and keep asking questions! We tend to learn things faster that way.
__________________
There's no way for you to know if what I'm saying is true unless you know what the truth is, and there's no way for you to know what the truth is unless there is a truth that you can know. -- Frank Peretti
Jeremy Davidson is offline   Reply With Quote
Old September 28th, 2005, 05:36 PM   #3
New Boot
 
Join Date: Sep 2005
Posts: 15
Quote:
Originally Posted by Jeremy Davidson
Not to worry, you are not a complete idiot.

Unfortunately, however, I don't believe it can be done. If I remember correctly, phantom power is typically 48v at only a few milliamps, so it would not be able to actually power such a device as it was never intended to run more than a tiny mic capsule and preamp. At 12 volts and 6 watts the current draw would be 500ma. Your best option for the LCD is probably to use a separate battery pack.

'Hope this helps, and keep asking questions! We tend to learn things faster that way.
You are absolutely right!

Phantom power is applied, usually, across both lines of a balanced microphone input via well matched 10 to 12 Kohm resistors, such that it is perfectly balanced in regards to the two active audio lines. You can better visualize this if indeed, the microphone input was applied to an input transformer primary winding, where the 48 volts phantom power applied to a center tap on the winding - this power thus is of the same polarity and voltage going back to the microphone in perfect balance. (This method harks back to the days of vacuum tube amplifiers.) This method is seldom used today since most microphone amplifiers have eschewed the input transformer as such transformers are quite expensive and heavy. High quality solid state opamps do this job quite nicely today. Even so, when a transformer is used with a center tap application of phantom power, a rather high value resistor is used at the center tap so that if one side of the microphone line happens to get shorted to ground, little harm is done, as little current can thus flow in the short circuit.

In the microphone, similar resistors are then used to render this very low power to power the tiny amplifier needed to amplify the very tiny signal produced by the condenser head in the microphone. Older microphones may also use a transformer with a center tap to then recover the phantom power to power the condenser mics amplifier. Other older condenser microphones had a separate power supply, rather then the phantom power set-up, which applied upwards to 300 volts to the condenser head! Some of the older German Telefunken condenser mics were this way. But I ramble here, sorry. :)

In any case, attempting to use the 48V phantom power for other uses that require greater current would be out of the question as you say.

Look at me, this old retired electronics technician reveals his age here!

William Putnam
William Putnam is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

Professional Video
(800) 833-4801
Portland, OR

B&H Photo Video
(866) 521-7381
New York, NY

Z.G.C.
(973) 335-4460
Mountain Lakes, NJ

Abel Cine Tech
(888) 700-4416
N.Y. NY & L.A. CA

Precision Camera
(800) 677-1023
Austin, TX

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > Canon EOS / MXF / AVCHD / HDV / DV Camera Systems > Canon HDV and DV Camera Systems > Canon XL and GL Series DV Camcorders

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



Google
 

All times are GMT -6. The time now is 12:47 PM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2017 The Digital Video Information Network