Input Connection; Unbalanced Input Wiring; Balanced Input Wiring; Subsonic Filter Capacitor Values - Crown Com-Tech CT-1600 Reference Manual

Com-Tech 200/400/800/1600 Power Amplifiers
tween the positive (+) terminals of both channels.
CAUTION: When Parallel-Mono wiring is installed, do
not attempt to operate in Dual or Bridge-Mono mode
until the wiring is removed (especially the jumper wire).
Failure to do so will result in high distortion and exces-
sive heating.

3.3.2 Input Connection

The balanced inputs have a nominal impedance of
20 K ohms (10 K ohms unbalanced) and will accept
the line-level output of most devices. The factory-in-
stalled P.I.P.-BB provides a balanced three-terminal
input barrier block for each channel (see Figure 2.2).
Optional P.I.P. modules like the P.I.P.-FX, P.I.P.-FXQ
and P.I.P.-FPX can provide female XLR connectors,
phone jacks and phono (RCA) connectors. Various
P.I.P.s are also available which provide a wide range
Shield connected
Floating
to ground terminal
source
+
Output
2-wire line cord
(or battery power)
Grounded
Shield not connected
source
at this end
+
Output
3-wire grounded line cord
(or other ground connection)
Floating
source
+
Output
2-wire line cord
(or battery power)
Grounded
source
+
Output
3-wire grounded line cord
(or other ground connection)
Fig. 3.8 Unbalanced Input Wiring
+
–
INPUT
+ –
INPUT
+
–
INPUT
Shield connected to both
negative (–) and ground
input terminals
+ –
INPUT
Input ground
terminal not used
Note: If two or more channels with
the same input ground reference
are driven from the same
floating source, connect
Floating only one shield to the
source chassis.
source
+
Output
–
2-wire line cord
(or battery power)
Grounded
Shield not connected
source
at this end
+
Output
–
3-wire grounded line cord
(or other ground connection)
Fig. 3.9 Balanced Input Wiring
of input signal processing features (see Section 8).
Proper input wiring depends on two factors:
(1) whether the input signals are balanced or unbal-
anced, and (2) whether the signal source floats or has
a ground reference. The following illustrations provide
examples of recommended connection techniques for
each type of signal source.
S O L V I N G I N P U T P R O B L E M S
dB
0
–5
–10
–15
1 Hz 10 Hz
Fig. 3.10 Subsonic Filter Capacitor Values
Sometimes large subsonic (subaudible) frequencies
are present in the input signal. These can damage
loudspeakers or step-down transformers by overload-
ing or overheating them. To attenuate such frequen-
cies, place a capacitor in series with the input signal
line. The graph in Figure 3.10 shows some capacitor
values and how they affect frequency response. Use
only low-leakage capacitors.
Another problem to avoid is large levels of radio fre-
quencies or RF in the input signal. Although high RF
levels may not pose a threat to the amplifier, they can
burn out tweeters or other loads that are sensitive to
+ –
INPUT
+
–
INPUT
100 Hz 1 kHz
Frequency
Page 17
10 kHz