[Elecraft] K3 Line In hum

[Jack Smith]

Same effect can be seen in the output transformers since none of the 
K3's transformers are magnetically shielded.

I found 20 to 25 dB difference in induced hum by rotating the K3 in 
three dimensions. Whether  the hum minimization orientation puts the K3 
in a usable position is another question.

Another alternative is to replace the transformers with shielded 
versions, assuming space on the PCB is available and a shielded 
transformer with the same electrical specifications and footprint is 
available.

In my case, the hum field is only (so far) in the basement area of my 
workbench.

Jack




Gerard Jendraszkiewicz wrote:
> Hello,
>
> I wonder if anyone else experienced this type of problem and has a 
> possible solution ?
>
> Independent of any connectiions I found out a 50Hz hum on my Line-In 
> audio. After a long investigation I figured out
> it was a coupling with other transformers external to the K3.  The 
> transformer of my ampliflier ( 10" away from my K3 ) couples an audible
> 50hz hum into the Line-In input. It seems the small isolation 
> transformer in the Line-In line is prone to pickup of
> 50Hz/60Hz magnetic field. Always I'm able to simulate it with other 
> transformers.
>
> Increasing the distance from the K3 to the amplifier is not an option as 
> my shack space is limited. Any sugestions to prevent it?
>
> 73 Harry DM5TI
>
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