9
to one another. If you must use a common path for all cables, use a
4.Before changing input connec- tors or wiring, turn the amplifi er level controls all the way down (counter- clockwise).
5.Before changing output connec- tions, turn the amplifi er level down and the AC power off to minimize the chance of
1.2.2 Solving Input Problems
Infrasonic (Subaudible) Frequencies
Sometimes large infrasonic (sub- audible) frequencies are present in the input signal. These can damage loudspeakers by overloading or overheating them. To attenuate such frequencies, place a capacitor in series with the input signal line. The graph in Figure 1.3 shows some capacitor values and how they affect the frequency response. Use only
capacitors.
Radio Frequencies (RF)
Figure 1.3
Subsonic Filter Capaci- tor Values
Figure 1.4
Unbalanced RFI Filters
Another problem to avoid is the presence of large levels of radio frequencies or RF in the input signal. Although high RF levels may not
pose a threat to the amplifi er, they
can burn out tweeters or other loads that are sensitive to high frequen- cies. Extremely high RF levels can
also cause your amplifi er to prema-
turely activate its protection circuitry, resulting in ineffi cient operation. RF
can be introduced into the signal chain from many sources such as
local radio stations, tape recorder bias and digital signal processors (DSP). To prevent high levels of input RF, install an appropriate
Some examples of unbalanced wiring for
For balanced input wiring use one of the examples in Figure 1.5. Filters A, B and C correspond to the unbalanced fi lters above. Filter D also incorporates the infrasonic fi lter described previ- ously.
Hum and Buzz
If you have noticeable hum or buzz
in your system, you may want to
check your cable connections to
see if the unwanted noise is being
introduced via a ground loop. To
determine the proper wiring, fi rst
check whether the output from
your source is unbalanced or bal-
anced (if you don’t know, refer to
the unit’s back panel or Operation
Manual). Next, determine if the source’s power cable is fl oating
(ungrounded,
cable type, refer to the applicable wiring diagram in Section 1.2.1.
Amplifier Application Guide