When I was a young broadcast engineer I learned that audio shielding
should only be at
one end of the cable. When wiring interconnection blocks, the shield was
connected to the
ground bus installed around the connection block, copper strap carried
it to earth.
The other end of the cable was ungrounded, just the red and black of the
pair were connected,
some bales used white and black, go figure.
The same for microphones, through XLR connections, the mike only
"grounded" at the jack in
the wall/equipment/mixer/tape deck.
Some of the facilities that apprenticed my craft still used AC type
plugs for mikes, XLR was just
being berthed and was a god send, singing in the streets, etc.
The object of all this was to prevent stray power/ AC/ stray current
differences between equipment
from finding a home through the shield, thus inducing some voltage on
the wires within, hence the
dreaded /hum/.
I can only deduce this ongoing thread on impedance, ground loops (which
in reality is what we
have here), etc.I am sure the learned folk on this forum have duly
impressed me with their
great wisdom/knowledge/education/reading/use of big words/etc and all,
resulting in the techno
babble that has herewith presented itself.
Just keep it simple for the old feeble minded OOOT's like me ... we want
to keep out the hum.
73
ed K0KL
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|