On Fri, 15 Feb 2013 16:37:47 -0800 (PST), klem kedidelhopper
wrote:

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. No way is it "very low" unless
something is broken or you're running at drastically reduced volume.
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. This can be a problem when someone actually does
use cheap, junk small gauge wire that sometimes simulates a fuse.

How it works:
http://rane.com/note136.html
http://www.crownaudio.com/media/pdf/amps/138905-1_10-05_constant_voltage.pdf

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558