[RFI] Hum in Bose QC2 headphones

[Jim Brown]

On Wed, 14 Jan 2009 00:29:28 -0500, Gary Smith wrote:

> Turning 
>off the AStron Linear supply to the K3 & bench does nothing to 
>attenuate the hum. Turning off the Titan 425 did nothing. 

You may have a magnetic field problem due to wiring errors in your 
AC power distro. There must be ONE, BUT ONLY ONE, bond between 
neutral and ground in any power system, and that bond must be at the 
building service entrance. You're only permitted another bond if 
there's another SYSTEM -- that is, a local distro transformer or UPS 
with a transformer output. That SYSTEM would need an additional 
bond. 

Study the material on my webpage about power systems and the power 
point on Ham Interfacing to get some ideas about finding what sounds 
like a magnetic field problem. 

73,

Jim K9YC