[Elecraft] Modulation interference KPA100

[Harry de Grood]

Hello,

I just finished the KPA100 without problems.
With the first test I hear that the sound of the modulation is not good, it 
looks like a interference with a 50 Hz sound.
That is always, with 1 Watt output or 100 Watt output, it make's no 
difference. My powersupply is good.
I check the alignment specialy the bias, that is good!
I was listning to the modulation with the KPA100 next to the K2 and 
everything was normal.
Hear is the problem: With the KPA100 in the K2 the sound is bad!
What can I do? I check the cables, everything is normal.

Harry PA3CWQ.