[Elecraft] Re: K3 Audio

[Joe Subich, W4TV]

> On Wed, 6 Aug 2008 09:32:55 +0200, Koppendorfer Klaus wrote:
> > did you use the line out ?? The Line Output
> > transformers of the K3, saturate at normal program levels
> > try Headphone out on Frontplate and you will see no Harmonic´s

Having heard this several times I did some research: 

Yes, it is possible to force the "Line" output into distortion 
but you literally have to force the K3 to distort.  If AGC is 
turned on, I do not see distortion/saturation at any level of 
input signal or any level of "Line Out."  If I turn off the AGC 
and crank the "Line Out" setting to 100, audio will be distorted 
with the 50 uV signal from an XG-2.  

Adjusting the Line Out level while watching the audio output 
with a scope and audio spectrum analyzer shows that there is 
no issue as long as the audio level remains below 1V peak (.7V 
RMS).  With an S9 signal (50 uV, preamp off), the Line Out 
voltage reaches .7V RMS with CONFIG:Line Out set to about 12. 

All of this is consistent with the K3 Manual which says: 

  | LIN OUT settings above 10 are usually not necessary, 
  | and can in some cases cause overloading of either the 
  | K3’s output transformers or the PC soundcard inputs
  | (typically on noise peaks). Either could degrade the 
  | performance of digital demodulation software.

For the benefit of W8JI ... saturation is a good description of 
the behavior.  When adjusting the Line Out level above 1V peak, 
any single tone in the audio spectrum appears to be clipped 
at the 1V level. Although this could be due to clipping in the 
audio amplifier, given the manual warning, transformer saturation
appears to be the more likely explanation. 

73, 

   ... Joe, W4TV