Power Supply for Carbon Mic

[emrr]

"A large size 4 1/2 volt "C" Battery will provide several hundred hours service."

http://www.google.com/products/catalog?client=safari&rls=en&q=4.5+volt+battery&oe=UTF-8&um=1&ie=UTF-8&tbm=shop&cid=16053622390004316895&sa=X&ei=Ylx2TsvpFYXc0QHSio1g&ved=0CEsQ8gIwAA

 

[VoiceOverMike]

Carbon Mics are noisy, that's the joy of them.

 

[prestok10]

Hi.

I recently acquired an Electro-Voice Model 100 carbon mike, and I am itching to try this myself. I think I know even less about electronics than you do, but I have some techie friends who are willing to help me. Have you made any more improvements to your circuit since your last post?

 

[joro]

Is the Electro-Voice Model 100 single button or dual button? I'm guessing dual. There should be no improvements, only variations. You can add a transformer, but in it's simplest form what is explained in the previous posts is the most straight forward. Give it a try. Take a 9V battery, 1K resistors to limit current, 10uF capacitors to block DC and you can add the 100K resistor if you want, and that's it. Changing values of the 1K resistors will just give you different output level and changing the capacitor value will just change the low frequency roll off point.

 

[coriolis]

About phantom power: Does that 48V standard not come from telephones anyway?
What I mean is: Aren't most old(er) handsets powered by 48V?
Or did I get something wrong?

 

[abbey road d enfer]

About phantom power: Does that 48V standard not come from telephones anyway?

Only very remotely. Broadcast stations had a lot of telephone equipment, so 48v PSU's and batteries were quite common, and it was also used for all sorts of ancillaries like "Red" light sign; that's why it was also chosen for phantom powering in studios, as opposed to 12V "T" for location recording.

What I mean is: Aren't most old(er) handsets powered by 48V?
Or did I get something wrong?

Yes and no. Carbon mics are current-driven. 48V is the starting point, but the plain old telephone system operates on a current loop; line current is regulated at about 20mA IIRC, so that's more or less what the capsule expects. It doesn't mean it wouldn't work with much lower current but the sensitivity and S/N ratio may fall rapidly.

 

[coriolis]

Thanks for clearing that up a bit