Mike,
That sounds like hum, buzz and noise being picked up by the connecting
cables.
I would suggest that you follow Jim Brown's K9YC advice on bonding.
With heavy wire or braid, bond the various boxes following the path(s)
of the interconnecting cables and coax. The bonding will conduct that
noise onto the outside of the various enclosures instead of allowing the
cable shields to conduct that noise into the boxes and onto the ground
plane.
In days of old when connectors were mounted directly on the enclosure,
this sort of thing was not a problem - noise pickup on the cable shields
was conducted onto the outside of the enclosures and did not pose a problem.
In today's world, the shields of interconnecting cables are connected
directly to the ground plane inside the box containing the circuits (pin
1 problem), and any noise picked up by the cable shield is transmitted
to the circuit ground plane. The bonding routes much of that noise onto
the outside of the enclosure and keeps it away from the circuits inside
the box.
73,
Don W3FPR
On 12/13/2016 6:33 PM, Mike Murray wrote:
Since starting to use my K3/0 I've been bugged by a "buzz" coming from the
speakers that I haven't been able to identify. Turning the volume up
overrides the noise, but it's still there. I've tried 3 different power
supplies with no change, including the one supplied by Elecraft. Here's a
recording of what I'm hearing:
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