© 2003 TDM Audio, Inc.
Graphic Equalizer Owner’s Manual
Page 15
correct supply voltage and frequency (US models are set up for 110 VAC at 60 Hz). Using a unit
designed for 220 volt operation with a 110 volt outlet can cause distortion.
One of the most common causes of distortion is improper gain staging. That means that some
piece of equipment is operating at much lower than unity gain (the signal coming out of it is a lot
lower than what is being fed in). Under these conditions, there is often some piece of equipment
that must provide a very hot signal output to compensate. This can cause distortion in the output
stages of this unit, or in input stages of the unit that it is driving. Check the +10dB red indicator
light on the face of the unit. If this light is flashing often or stays on constantly then either the
signal feeding the unit is too hot or the level of the unit is set too high. Excessive boosting of
frequencies that are very hot in the program source can also cause distortion in the equalizer.
If the unit is plugged into the correct power source, the signal feeding the unit is clean, your gain
staging is normal, and you are still getting distortion, contact your vendor, or call TDM for
support and/or service (see
Contacting TDM
).
Excessive Noise
TDM 30GE series equalizers have an excellent signal-to-noise ratio. If you hear excessive noise
in your system, try to determine its origin systematically. Remove each piece of processing gear
from the signal chain one at a time until you hear the noise go away. If none of the signal
processing units is the cause of the noise, then the noise is probably present in your signal
source. You can remove the TDM 30GE series graphic equalizer from the signal path by simply
pressing the hard-wire bypass switch.
If you suspect that the TDM 30GE series equalizer is the cause of your noise problem, make sure
the unit is plugged into the correct power source. Read the rear panel of the unit to determine the
correct voltage and frequency (US models are set up for 110 VAC at 60 Hz). Using a unit
designed for 220 volt operation plugged into a 110 volt outlet can cause very noisy operation of
the unit.
Make sure your gain staging is correct. If some unit in your system is running at a very low gain,
or if your signal source is weak, you may be running some other unit at a very high gain to
compensate. Some audio equipment produces excessive noise when running at gain levels higher
than unity.
If you check all of these possible causes and you still can’t resolve the problem, contact your
vendor, or call TDM for support and/or service (see
Contacting TDM
).
60 Hertz Hum or Buzz
60 Hertz hum or buzz in a system can be extremely difficult to track down because it is usually
not a problem with any one piece of equipment. It is usually caused by how the entire system is
connected and grounded.
To fix a hum or buzz in a system, suspect any piece of equipment that gets a ground connection
from more than one place. These problems are called “Ground Loops” and the technical
explanation of why they cause problems is that there is actually an AC voltage difference
between the two different grounds. The problem is most often caused by a single piece of
equipment grounded to two different power sources that are located some distance apart. For
example, a mixing console is plugged into a grounded outlet at the back of an auditorium, and
