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Warning::::externally-polarized condenser mics Condenser Microphones
Old 29th December 2010
  #1
Here for the gear
 

Warning::::externally-polarized condenser mics

According to Jay Rose:

"Externally-polarized condenser mics used for professional productions, often costing in the $1000 Range, usually have internal transformers with 500 ohm outputs. An exact match isn't necessary, because the output power isn't generated by air molecules, but anything over 2 k ohm might cause problems"

"AGAIN, almost any XLR mic-level input qualifies"

Which i assume would include: Sennhieser 416's, Schoepes Collete, and Schoepes CMIT 5u , and Nuemann's


Care to comment?
Old 29th December 2010
  #2
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I came across this problem before I started using a high-quality microphone, I rented, with my low-quality field recorder. I didn't want to damage the microphone somehow, but not matching the output power correctly.

Would that actually be the consequence?- "damaging the microphone"??? Jay rose was incredibly vague on describing the consequence of an inadequately matched, but completely "balanced" 48p microphone system...
Old 29th December 2010
  #3
Here for the gear
 

I came across this problem before I started using a high-quality microphone, I rented, with my low-quality field recorder. I didn't want to damage the microphone somehow, by*** not matching the output power correctly.

Would that actually be the consequence?- "damaging the microphone"??? Jay rose was incredibly vague on describing the consequence of an inadequately matched, but completely "balanced" 48p microphone system...
Old 29th December 2010
  #4
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mark.frost's Avatar
 

from:

Phantom Power Explained

"The typical value of the two resistors is 6.81k-ohm. More than just the audio and the source impedance (of pin-2 and pin-3) must be balanced. The "phantom" resistors must also match to a tolerance of at least 1% — .1% tolerance would be even better.





The resistor color code is interpreted as follows. The first three stripes from left to right are the significant figures. For example: 1st stripe (blue = 6), 2nd stripe (gray = 8), 3rd stripe (brown = 1). The 4th stripe is the decimal multiplier, in this case brown = one "zero" instead of the number "one." The fifth stripe is the tolerance: brown = 1%. So, from that you can conclude that the value is 6.81kW . Low-noise metal-film resistors were used in Figure One along with a "local" capacitor to filter any noise."
Good luck!
Old 29th December 2010
  #5
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mark.frost's Avatar
 

a way you could prevent damaging the microphone, is by using a
Schoepes MDZ10/MDZ 20, it'd run you $100 though:


The MDZ can also prevent the input impedance of a preamp from loading down a microphone; with it in place, the minimum load impedance for a CMC-series amplifier is reduced from 600 to 200 Ohms. It can also be useful when driving transformer-equipped inputs designed for 200 Ohm sources, which may develop high frequency response errors when driven by much lower impedances, particularly if the input transformer has a high turns ratio.
Old 29th December 2010
  #6
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honestly, I don't think damaging the mic is gonna be the issue here.

Also------------> I don't want to spend $100 on a microphone I'M JUST RENTING... Even if it is a CMIT5!!!

They never told me anything about this @ Location Sound in Los Angeles- the place i rented the mic from.Although some people say they're very knowledgeable.

They just said "Just plug and play, you're Fostex FR 2 Le should be fine".
Old 29th December 2010
  #7
Gear Guru
 
John Willett's Avatar
 

Warning::::externally-polarized condenser mics

The Sennheiser MKH range are not like what the OP quoted at all. They are RF condensers, the circuit is inherently balanced from the start and does not need any transformer or electronic balancing circuit at all as it's already balanced.

The MKH 416 is ten Ohms, if my memory serves me well, and is great for driving very long lines (and the MKH 60 can easily be converted to ten Ohms if it's needed for outdoor sports use on long cables).

Normally the recorder impedance is 5 to 10 times the mic. impedance, this is normal. I don't know of any modern condenser mic. that would be damaged by a normal mic. input with phantom power (valve mics excluded, of course, as they need a separate PSU).



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