A Detailed Guide To Constant-Voltage Audio Systems  June 20,
2013, by PSW Staff  av systems  Electric power companies have a
good idea that has been applied to audio engineering. When they
run power through miles of cable, they minimize resistive power
loss by running the power as high voltage and low current.  To
do this, they use a step-up transformer at the power station and
a step-down transformer at each customer’s location. This
reduces power loss due to the I2R heating of the power cables.
The same solution can be applied to audio communications in the
form of a constant-voltage system (typically 70 volts in the
U.S. and 100V overseas).  Such a system is often used when a
single power amplifier drives many loudspeakers through long
cable runs (over 50 feet). Some examples of this condition are
distributed speaker systems for PA, paging, or low-SPL
background music.  The label “constant voltage” has been
confusing because the voltage is really not constant in an audio
program. A better term might be “h