On Tue,5/30/2017 1:57 PM, Carl Moreschi wrote:
I don't think 8 ohm headphones were correct. I think much higher
impedance phones forces you to turn the volume up and drown out the hum.
8 ohm phones are fairly rare. Most are in the range of 50-600 ohms.
Question to the original poster -- is what you hear HUM (pure 60 Hz) or
BUZZ (harmonics of 60 Hz)?
Hum is most often stray magnetic field from a big power transformer.
Buzz is most often related to leakage current from the AC power system.
Leakage current is best controlled by proper bonding -- every chassis in
the shack bonded to every other chassis, that combo bonded to all the
other grounds in your home, all gear plugged into outlets that use the
same green wire back to the panel (or from outlets whose green wires are
bonded together at the outlet).
One wiring problem within equipment I've run into is related to
connection of the green wire from the power plug, or to the return of
the power transformer center tap to the chassis. If either of those
connections is to the shell of headphone jack, it could cause what
you're hearing.
73, Jim K9YC
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