[Elecraft] Koss SB-45 Headset, update on comfort

[n9tf at comcast.net]

Gus, 
  
I think the term bias, or bias voltage is a pretty generic term when meaning applying a voltage or current to turn on a device, in this instance a microphone element that requires voltage to operate. 
  
http://www.learningaboutelectronics.com/Articles/What-is-bias-voltage 
  
73 Gene, N9TF 

----- Original Message -----

From: "Augie \"Gus\" Hansen" <augie.hansen at comcast.net> 
To: elecraft at mailman.qth.net 
Sent: Wednesday, January 6, 2016 1:02:58 PM 
Subject: Re: [Elecraft] Koss SB-45 Headset, update on comfort 

Hi Jim, 

> Electret and dynamic mics are equally good for ham radio. Use whatever 
> comes with the headset you like and be happy. All that matters is that 
> electret mics need bias turned on and dynamic mics do not. 

Do you know why Elecraft calls the power provided to an electret element 
BIAS? Unlike the large form condenser microphone elements that need both 
polarizing potential and preamp power, usually provided via a "phantom 
power" circuit, an electret element is permanently polarized. The power 
applied via the phantom circuit is actually providing only the drain 
voltage for the FET preamp in the electret microphone capsule, not any 
kind of biasing voltage. 

Of course we have similar terminology used in systems that provide 
control voltages or operating power to remote equipment: The so-called 
BIAS-TEE used to inject and extract power over a coaxial cable, for 
example. 

I haven't found any official documentation for these types of circuits 
that uses the BIAS moniker. Are there any references that you might 
point to? 

Cheers, 
Gus Hansen 
KB0YH 

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