External speaker hum with K3

[Greg Mason]

I connected a pair of Bose Companion 2 computer speakers (magentically shielded with amplifier) to my K3 and was rewared with a strong hum.  I have ensured that the speaker setting is correct and I am using the Bose stereo connector.  I also get the same result with the line out at various settings.The speakers work fine with my iPad and computer, so they are not the problem.  I finally connected them to the headphone jack and they work very well.  The right channel unit has a head phone jack, so I do not lose the muting functionality.  What am I missing with the connection to the speaker-out on the K3, which I would prefer to use?
 
Greg Mason
VE4AMN
[hidden email]
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[Jim Brown-10]

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
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[Bill Frantz]

This probably isn't the problem being experienced, but I found
when I took the audio output of the ICOM 706 in my car and ran
it through the car stereo system there was a strong low
frequency "hum" when listening to a local 2M repeater. After a
bit of thought, I am blaming the 151.4 Hz CTCSS tone sent by the
repeater, which is too low for the small speaker in the radio,
but comes out strongly with the car stereo. I haven't had a
chance to install a high pass filter in the audio line.

Cheers - Bill, AE6JV/OK

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