[Elecraft] headphone impedance

[Jim Brown]

On Mon,12/28/2015 10:08 AM, Barry N1EU wrote:
> I believe this also means that the K3 headphone output circuit will
> deliver 10X power (with fixed V, P~1/R) into a 30-ohm headphone as a
> 300-ohm headphone, so at some point the amp might clip as you raise
> the headphone impedance?

Only if you crank the headphone output too high. My 1V example is simply 
the maximum sine wave output at clip, and that value is typical. When 
you turn down the headphone gain, you reduce that voltage. I don't 
recall the spec for the K3. In your 30 ohm headphone example, you would 
probably not need to crank the gain nearly as high, so the output 
voltage would stay below clip. The exception might be if the operator 
has significant hearing loss, so was driving the headphones very hard.

73, Jim K9YC