[Elecraft] K2/headphone impedance compatibility

[Rick Shindley]

The K2 splits the monaural audio signal for stereo headphone operation, but
employs an RC filter in each of the headphone circuits.  The series
resistance in each circuit is 82 Ohms.  Using a 32 Ohm headphone element
means that only 28% of the available audio signal voltage is impressed on
each headphone element, and that's if the audio signal frequency is below
the 882Hz cutoff frequency of the RC filters.

I am using a cheap 32-Ohm stereo headset and the audio level is about
adequate.  I would expect a 300 Ohm headphone would be much louder without
the need for a voltage step-up transformer.

Rick KC0OV
K2 1360