What is high impedance

Posted by David Christ on Feb 08, 2010; 9:47pm
URL: http://elecraft.85.s1.nabble.com/K3-in-a-cw-pileup-needs-work-tp4523884p4537337.html

After Lyle's comment (reproduced below),  there has been been concern
expressed about headsets of 120 to 600 ohms.  A close reading of
Lyle's words indicates that higher impedance is only a problem if
there is a need to increase the AF gain too much.  As long as you
don't have to crank the AF gain way up there shouldn't be a problem.

I think there is also some confusion about what high impedance means.
The common WW II aircraft headset came in two versions  High Z at
4000 ohms and Low Z at 600 ohms.  By that standard 120 ohms is very
low and 600 is still low.

If your AF gain is at 3 o'clock maybe your earphones or ears have too
high an impedance.

David K0LUM

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Note that the headphone audio path of the K3 is designed for 32-ohm and
lower headphone impedances.  Higher impedance phones provide less audio
for a given transducer efficiency.  Cranking up the AF gain to
compensate can lead to clipping-related distortion.

73,

Lyle KK7P
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