[TenTec] Century 21 audio hum

Jim Brown k9yc at audiosystemsgroup.com
Tue May 30 20:43:51 EDT 2017

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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