9
BRIDGE MODE SELECTOR SWITCH
When a 2-channel amplifier is operated in the Bridge mode, it is converted into a single-channel unit with a
power rating equal to the sum of the power rating for each channel, at a load of twice that of the single-chan-
nel rating. For example, the CPX 4 is rated at 1600 Watts RMS per channel into 4 Ohms. The Bridge rating is
3200 Watts RMS into 8 Ohms. Bridge mode operation is accomplished by placing the MODE switch in the
BRIDGE position, and using a twist lock connector wired for bridge mode on the channel A output, and using
the CHANNEL A input. All CHANNEL B input functions are defeated and serve no purpose now. Bridge mode
operation can be used to drive sound distribution systems in very large public address applications. Another
common use for the Bridge mode is in subwoofer applications where very high power levels are required to
reproduce extremely low frequencies with adequate headroom. Such enclosures usually contain 2 or 4 loud-
speakers to handle the power levels involved. When using Bridge mode, the connected enclosure impedance
must be 4 or 8 Ohms — never below 4 Ohms.
CONNECTING INPUTS
Input connections are made via the 3-pin XLR (pin 2+) or 6.3 mm plug “Combi” connectors on the rear panel of
the amplifier. The inputs are actively balanced.
The input overload point is +28 dBu.
CONNECTING OUTPUTS
The CPX4 has twist lock output connectors. Channel A and Channel B may be accessed individually with 2
conductor connectors, with (+) at terminal 1+ and (-) at terminal 1-. A 4 conductor twist lock may be used on
the channel A output, with channel B appearing at terminals 2+ and 2-. For BRIDGE mode, use only the channel
A twist lock connector, and the (+) output is at terminal 1+, and the (-) output is at terminal 2+, which is fed from
Channel B output.
The input XLR connectors are wired according to standard practive for balanced interconnections, with pin 2 (+),
pin 3(-) and pin 1 ground. The TRS connectors are wired with Tip (+), Ring (-), and Sleeve ground.
*
17
Rear Panel
16
GCL
Crest’s patented GCL (Gain Comparator Limiting) limiter circuit enables the sound technician to maximize the
performance of the amplifier/speaker combination by preventing the power amplifier from clipping. When
the onset of clipping is detected, the limiter engages to prevent damage to the loudspeakers and
degradation of sound quality. For this reason, GCL should always be enabled.
Regardless of what connections
are used, the minimum parallel speaker load
should always be limited to 2 Ohms per channel, or 4 Ohms
when in BRIDGE mode. Operation at Loads of 4 Ohms
per channel, or 8 Ohms BRIDGE mode, is more desirable
for sustained operations because the amplifier will run much
cooler with this load. Operation above 4 Ohms per channel
and even open-circuit conditions can always be considered
safe, but sustained operation at loads below 2 Ohms
could result in temporary amplifier shut down due
to the thermal limit circuitry.
WARNING.
**
Summary of Contents for CPX 4
Page 17: ......
