[Elecraft] Harmonic Distortion and Audio Intermodulation in K3's LIN OUT Port

[Jack Smith]

I've completed a series of detailed measurements trying to understand 
why my K3's LIN OUT port exhibits greater distortion and anomalies than 
found in the headphone and speaker ports.

Details are at 
http://www.cliftonlaboratories.com/elecraft_k3_receive_audio.htm

What I found is that the 604 ohm resistor between U29's output amplifier 
stage and the TTC-108 transformer primary winding forces the TTC-108 
isolation transformer to operate in a regime where the performance 
improving effects of a zero ohm driving source are not available. Hence, 
the TTC-108's 0.5% THD performance significantly limits the LIN OUT 
ports performance.

I've also provided a  theoretical parts value change that should improve 
the LIN OUT distortion and intermodulation. I have not implemented this 
change in my K3, but the external circuit mockup I used for testing 
strongly supports the change.

I've supplied my measurements to the gurus at Elecraft for their 
consideration. If my data and  recommendations make sense, I would 
expect confirmation from Aptos, after they have time to think it over 
and consider possible side effects.

Jack K8ZOA
www.cliftonlaboratories.com

 
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