22
H
Hu
um
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The exceptional audio
performances of your PL-P allow
you to re-discover the pleasure of
listening to vinyl LPs, and will give
you hours of exceptional listening
pleasure. However, you can only
benefit from the total quality of your
PL-P if it has been correctly
installed.
The cables that connect the phono
cartridge of the turntable to the PL-
P carry extremely low-level signals,
and any error in the connection of
the system is likely to create hum
caused by AC ground loops. To
deal with this, the PL-P is designed
to cover a number of technical
points, which should be well
understood in order to achieve an
optimal configuration. Before going
into details, the first step is to be
sure that all the various units in the
system (turntable, PL-P, amplifier,
CD-player, etc.) are powered
correctly.
As a preamble, we will explain the
hurdle. Any wire has an electrical
resistance, and all currents passing
through a resistance create a drop
in voltage. Depending upon where
the voltage drop occurs, you will be
confronted with more or less AC
hum.
Normally, the AC network that
powers your equipment is made up
of three separate conductors, these
being the ground/earth, the neutral
and the phase, the latter two allow
the passage of energy to the device
being powered. The latter two wires
are not floating; the phase wire,
which should not be touched for risk
of electric shocks, carries a high
alternating potential (110 V or 220
V), whereas the neutral wire is very
close to the ground/earth and can
normally be touched (in principle!)
without any risk. Normally these two
wires carry an identical current, one
being the return of the other.
The third wire, the ground/earth,
allows all the chassis of all the
equipment in the installation to be
linked together. It constitutes a
security in the event that one of the
pieces of equipment has a break in
the isolation of the phase.
In principle, this wire carries no
current, and therefore according to
the theory above, there should not
be any difference in potential
between different points along its
length. Unfortunately, this is not
always the case.
In fact, the demands of modern
regulatory standards regarding
high-frequency protection, create a
significant circulating current along
the length of this wire.
In addition, it is possible that
various pieces of equipment
connected to your AC network,
without being defective, present an
earth problem, which in itself
causes a loop current within this
precious earth wire. Finally there is
the most frequent case, where the
neutral and the earth wires are one,
and cause these currents to be
carried throughout your installation,
causing in most cases terrible AC
hum.
If you find yourself confronted with a
situation similar to that shown
Hum
