VERY EXCELLENT PRIMER ON ELECTRET MICS !!!! great job Augie.
Yesterday I hear a guy on 20, who was an"audio" guy, with inline
processors and mixers. He likes his old EV 664.style .( very
retro)...He bought an electret from Radio Shack...and gutted the
664...put in the electret and had a base station mic JUST AS GOOD AS
A ________...fill in the blank.....
Just grab any old nice looking gooseneck mike or lamp and install an electret.
The only problem with the electret is that USUALLY it is a flat
response microphone. If you want to eq it you can do it electrically
or mechanically by adjusting a baffle behind and or infront for the
element. (Mechanical is free, and adds no noise and is less rf
susceptible than a mixer or eq box)
have fun... yes we can fiddle with mics and speakers not just antennas,,,,,
bill
At 06:03 PM 8/5/2005, Augie Hansen wrote:
Hi Roland,
Because I have several Icom transceivers, I wired my K2 to match the Icom
microphone pin assignments for the audio circuit and PTT (I haven't wired
the up/down buttons, but may add them later). In addition to convenient
interchangeability, the output level of the Icom-compatible microphones
(hand, desk, and Heil boom set) is fairly high, making it easy to drive the
K2 to full output and run VOX without difficulty.
The electret condenser element in these mics requires power for the FET
preamp in the element. I wire a 2.2K resistor to the +5 volt available on
the K2 header to provide phantom power on the hot lead to the mic.
By the way, there is some confusion about the DC power required by electret
elements. It is not a polarizing voltage. A standard condenser element
requires a polarizing voltage (typically 48 volts is used) for the condenser
plus power for a preamp that raises the very low output level to something
useful. However, an electret is a permanently polarized condenser, where
permanent is a relative term. Most such elements are guaranteed to retain
adequate polarization for at least 10 years, but 100 years is not unexpected
in practice, without the need for any external polarizing source. (I'm still
using Radio Shack electret elements that I bought for less than $1.50 each
nearly 20 years ago. No problems.) A voltage of 2 to 10 volts is typically
required to power the built-in preamp, usually an FET stage. The K2 makes 5
volts readily available, whereas the Icom rigs provide 8 volts for this
purpose.
Let me know if you need more information on this topic.
Gus Hansen / KB0YH
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