On Feb 17, 8:49*pm, "Phil Allison" wrote:
"Jeff Liebermann"
*klem kedidelhopper



The music is distributed via 70V lines at very low level
throughout the building.

Methinks not. *The voltage on a 70v constant voltage speaker system is
(insert drum roll...) 70.7 volts rms.

** Absolute nonsense.

70V is the maximum voltage output from the amplifier and there is nothing
constant about it.

No way is it "very low" unless
something is broken or you're running at drastically reduced volume.

** Volume pots allow the level to be set at the operators convenience.

It is very common to have a low, background music level and a much higher
speech level for announcements.

The big advantage to 70v and 100v systems is that they can use cheap,
junk, small gauge wiring, such a CAT3 telephone wire for relatively
high power speakers.

** More nonsense.

The real advantages include the use of long cable runs with low losses and
having many distributed speakers - which do not need to be all of the same
rating type or level.

.... * Phil

To further explain this, the amplifier's, (which is located in one
building), output is taken off the 70 V tap, however as Phil alluded
to the voltage on the line could be and in fact in this case is very
low, ,just a few volts. This is all I need because, again this is VERY
low background music and the level seems to be satisfactory throughout
the building. As far as the lines being balanced, I'm assuming that
they still are as I have done nothing anywhere that I can think of to
cause an unbalance. As I mentioned before this balanced line output
leaves the amp on two pairs of a CAT3 cable. I used two pairs because
they are the main feed for all the speakers. This "main" cable runs
from this building underground through PVC pipe to the 66 block in the
other building. At that location all the other CAT3 wires also appear
on that block as well. On each cable that was reused the brown pair is
connected to a speaker. in a different room. These brown pairs are all
placed in parallel and then connected to the 70V feed. So this is all
well. It is not however the problem. The problem is occurring when I
try to sample the siren driver output from the alarm and apply it to
the low level input of the music amplifier. That's when I hear the
data noise which I'm certain is being picked up by the "antenna" which
is the sample wire and fed into the mic input of the amplifier.
Lenny