Re: Basic questions about microphones and mic preamp design...

From: John Woodgate (jmw_at_jmwa.demon.contraspam.yuk)
Date: 12/13/04 

Date: Mon, 13 Dec 2004 11:47:22 +0000

I read in sci.electronics.design that Ban <bansuri@web.de> wrote (in
<Vgevd.286921$b5.13995616@news3.tin.it>) about 'Basic questions about
microphones and mic preamp design...', on Mon, 13 Dec 2004:

The OP wrote:

>> * What is phantom power, do all microphones require it, and it is
>> only used in differential microphone connections?
>>
>
>It is only used with balanced lines. +48V, negative to Pin1(gnd),
>positive through 2 resistors 6k8 into both of the balanced conductors
>(Pin2 and 3).

This is correct, but electret mics are often 'line-powered'. One
arrangement is:
ASCII art; use Courier font

                              +----o-------o-+-4.7kohm------o +V
                     mic | |
                             |] +----100 nF----o audio
             +--------+------| FET cable
             | | |] pre-amp/mixer
      mic |O 470 Mohm |
    capsule | | |
             +--------+-------+---o-------o----------------o 0 V 

-- 
Regards, John Woodgate, OOO - Own Opinions Only. 
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

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