KLING & FREITAG K&F E 90 MK II - Manual (Page 12)

User’s Manual E 90 MK II
KLING & FREITAG GMBH ©1995 - 2006 Version 4.0, 02.11.2006 Page 12 of 22
7.2 Avoiding Ground Loops
7.2.1 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 connected 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.
7.2.2 Avoiding Ground Loops
If there is a loud humming or buzzing after the E 90 MK II system has been con-
nected, 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 audi-
ble, check if,
− the noise is caused by a ground loop before the power amplifiers / controllers
(e.g. mixing console, effects or equalizers).
− the system or parts of the system are connected to an "unclean" power sup-
ply - meaning one, which is also running large motors, or lighting systems. An
"unclean" supply voltage, electrostatic and electromagnetic fields can cause a
malfunction.
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 cen-
tral 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 dis-
tance 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 connect a filter in front of the audio equipment.
Warning