[Scott Dorsey]

mcp6453 wrote:
After 55 years in the audio business, I have encountered a strange
problem for the very first time. I set up a small mixer and two dynamic
mics for remote recording. Everything tested perfectly at home. When I
moved the setup to the remote location (an office building), there was
hum and buzz in both mics. Isolation the mics from all wall warts and
power supplies did not have an effect on the noise.

New mic cables. No change.
Different (dynamic) mics. No change.
Added dbx286s for each mic. No change.
Disconnected all external equipment from the mixer. No change.
Physically rotating the mics on the desk. Change.

You have a magnetic field somewhere, maybe from a large transformer nearby,
and the microphones are picking up magnetic field leakage. Moving the
location to the other side of the room might fix everything. Then again it
might not. You might also try an original Sennheiser MD421, which has a
bucking coil to reduce magnetic pickup.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."