[Elecraft] External speaker hum with K3

[Jim Brown]

On 7/25/2013 7:30 AM, Greg Mason wrote:
> What am I missing with the connection to the speaker-out on the K3, which I would prefer to use?

Do you hear hum (pure 60 Hz) or buzz (harmonics of 60 Hz)?  The most 
common cause of buzz is leakage current from the AC power system, and it 
is coupled into audio when equipment that has an unbalanced 
interconnection is plugged into different power outlets, and when that 
equipment is not bonded together.

The simple cure for buzz involves two steps. 1) Plug all the 
interconnected equipment into outlets that share the same "green wire" 
back to the breaker panel.  2) Bond from chassis to chassis of all the 
interconnected equipment with short, fat copper.

If you have hum, the most likely cause is a magnetic field, most often 
from a big power transformer or from a mis-wired AC power system.

73, Jim K9YC