[Elecraft] Appropriate Mic for K3 (new)

[Jim Brown]

On Sun,12/4/2016 8:36 PM, Don Wilhelm wrote:
> Ham microphones are the Electret type, pro-audio Condenser microphones 
> are different.

Yes, they are POWERED differently, but the vast majority (I'd guess 90%) 
of pro mics that are called condenser mics are electrets. BUT -- that 
powering system REQUIRES that they feed a balanced input and have 
"balanced phantom power." That system applies a positive voltage in the 
range of 18 - 48VDC through close-tolerance, equal value resistors to 
the two sides of the balanced signal circuit (pins 2 and 3 of the 
XL-connector) with return for DC going to the cable shield (Pin 1).

The unbalanced electret mics we use in ham radio only require a positive 
voltage as bias for a FET-follower stage that transforms the very high 
output impedance of the capsule to an impedance low enough to drive mic 
inputs. The balanced outputs of pro electrets have an additional gain 
stage with an output impedance low enough to drive a long mic cable.

48V phantom is applied through 6.8K resistors; 18V phantom is applied 
through resistors of lower value. Virtually all pro mics will work with 
48V, and most will work with 18V, but most non-electret condensers 
require 48V.

73, Jim K9YC