KLING & FREITAG K&F CA 1515-9 - Manual (Page 21)

User's Manual CA 1201, CA 1215-6 /-9, CA 1515-6 /-9
KLING & FREITAG GMBH ©1998 - 2015Version 4.0, 07.05.2015 Page 21 of 53
11.2 Avoiding Ground Loops
11.2.1 What is a Ground Loop?
Every component of a P.A. or Hi-Fi System has its own internal 0 V reference (ground). This point is often con-
nected to the protective earth connector (PE / Ground). If two or more units are connected to one another
with a line level audio cable, there may be a ground connection through the ground of the power supply
cable (yellow-green) as well as through the shielding of the audio cable. The voltage difference between these
two ground points causes audible interference to come from the speaker
11.2.2 Avoiding Ground Loops
If there is a loud humming or buzzing after the CA System has been connected, then check that a "ground
loop" has not been built into the system. Some power amplifiers and system controllers are equipped with a
"Ground Lift" switch. Set these switches to the "Lift" position one after the other. If the noise is still audible,
check if,
1. the noise is caused by a ground loop before the power amplifiers / controllers (e.g. mixing console, ef-
fects or equalizers).
2. the system or parts of the system are connected to an "unclean" power supply - meaning one, which
is also running large motors, or lighting systems. An "unclean" supply voltage, electrostatic and elec-
tromagnetic fields can cause a malfunction.
Please observe the following basic rules: Please observe the following basic rules: Please observe the following basic rules: Please observe the following basic rules:
− Never!!! try to avoid a ground loop by disconnecting or taping the ground contact at
the power connector! Extremely dangerous!
− If possible, only use high-quality audio appliances with balanced signal outputs and
with power cables with PE connectors.
− Use high-quality cables with good shielding.
− The point of ground for all connected components should merge at one central point.
The power connections should lead out in a radial manner from one point and not be
linked from one unit to the next.
− When installing appliances that create strong electrostatic or electromagnetic fields (large transformers,
switch-mode power supplies), maintain some distance from other audio appliances. In extreme cases, the
only solution is to create a completely independent "audio ground"; in other cases, it is sufficient to con-
nect a filter in front of the audio equipment.
Warning Warning Warning Warning