[Amps] 120 cycle hum from Henry 2K-4

[Jim Brown]

On Wed, 03 Mar 2010 13:45:23 -0500, johndtate at post.com wrote:

>Much of the hum was magnetic pickup and 
>moving things and better grounding solved that. 

Clarification. I can believe magnetic coupling as the cause of 60 Hz 
hum, but a connection to EARTH has NOTHING to do with magnetic 
coupling. Magnetic coupling requires a loop for current that couples 
to a signal path, and that couples with a magnetic field. 

If by "better grounding" you mean that you cleaned up wiring to 
eliminate that current loop, I can believe that. But that isn't 
"grounding." BTW -- magnetic coupling can also be reduced by putting 
the field and the coupled circuit at 90 degrees to each other. For 
example, by rotating the box containing the power supply, or by 
rotating the loop. Or my making the loop area smaller. 

73,

Jim K9YC