[Elecraft] [K3] K3 Rev C DSP with Low Freq Enhancement

[Paul Christensen]

> Juan, I think your 3rd harmonic measurement is the key. If you research
> audio fatigue you may find that odd harmonics are particularly troublesome
> and that they can cause audio fatigue even when the level is below what 
> you
> might consider audible.

Mike,

There may be several variables occurring here.  When I get back from a 
conference, I plan on making my own FFT measurements at the H/P jack 
regarding this effect.  It's possible that the intensity of distortion 
artifacts as measured by Jack Smith, and presumably what you're hearing, may 
be different among K3 samples.  Myself, I don't hear anything that brings 
about fatigue under any operating conditions.

Also, Rx audio response capabilities with the latest K3 firmware has evolved 
and additional low-end content is present that was not there in previous 
releases.  And so, one has to consider whether it was the change in 
firmware -- or the beta LPF board that is now responsible for the changes 
you're now hearing.  I have to believe that with some ops, the perception of 
fatigue is related to a previous lack of low-end to presence-band balance. 
More than anything, what brings fatigue to me is extended listening through 
a narrow audio passband.

Paul, W9AC