[Elecraft] What is high impedance

[David Christ]

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