Crest Audio CKI - Gain, Ground Lift, and STO Controls

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Operation
5
Gain Select Switch
The 3-position gain select switch on the rear panel to sets the overall gain of
the amplifier.The left and right switch positions set the amplifier for constant
gain of x20 (26 dB) or x40 (32 dB) respectively.The center position sets the
amplifier for constant sensitivity.In this position,a 0dBu (0.775 VRMS) input
signal will produce maximum power at the amplifier’s output.The standard
factory setting is for x40 (32dB).The specifications for a specific CKi models
in Appendix A contain more gain/sensitivity information.
Signal Ground Lift Switch
The signal source equipment should share the same AC ground as the ampli-
fier(s).In some cases,however,particularly if an amplifier is being installed in
an existing system,this may result in a ground loop,creating excessive 60Hz
hum at the amplifier’s output.If this happens,slide the ground lift switch on
the amplifier’s rear panel to the “open” (left) position.In this position,the sig-
nal ground is lifted from the chassis ground and is clamped to ± 0.6V.Do not
lift the ground if the amplifier and the signal source equipment are not on the
same AC ground! In a properly designed system,the amplifier should receive
its ground from the AC line cord to ensure safety and minimize noise.
Sequential Turn On/Off (STO)
CKi amplifiers come standard with Sequential Turn-On/Turn-Off (STO) cir-
cuitry.When the amplifier front power switch is set to “remote,” a single
SPDT toggle switch or two SPST momentary switches can be used to turn
the amplifier on and off.Using the same switch(es),additional amplifiers can
be turned on/off sequentially by daisy chaining the STO "Out" terminals of
one amplifier to the STO "In" terminals of a subsequent amplifier.The stan-
dard turn-on delay time between amplifiers is approximately 100ms;turn-off
delay time is 200ms. When using NexSys control with an amplifier equipped
with an NxEthernet or NxCobraNet module,these standard turn-on and
turn-off delay times may be modified in the control software.
Standard Sequential Turn-On/Turn-Off Wiring
For non-NexSys remote turn-on,a single SPDT toggle switch or two SPST
momentary switches can be used.In either case,the switch(es) are wired to
the “STO In” connector on the amplifier’s rear panel and the amplifier’s front
panel power switch must be set to “Remote.” The switch(es) should be wired
to close a connection between “Com” and “On” pins for turn-on,and
between the “Com” and “Off” pins for turn-off. The diagram below illus-
trates the circuit:
Gain
(.775V)
0dB
x40x20
The shield on a bal-
anced input line should
be grounded at one end
only (usually the sending
end),and it must never
be relied on to supply
AC ground to the ampli-
fier.
a
When using NexSys
control,hardwiring
for manual switch
closure between ampli-
fiers should be used cau-
tiously. If the switch clo-
sure output is wired up,
it WILL cause the next
amp to switch,regard-
less of which source
(hardware switch or
NexSys STO command)
has initiated the com-
mand.
+
Active
+ +
Output - Class 2 Wirin
g
In Out
On
Com
Off
On
Com
Off
Fault
N/O
Com
N/C
Gnd
In
Sequential Turn-On
Input
V-In
3.3V
Out
On
Off
Active
+ +
Output - Class 2 Wirin
g
In Out
On
Com
Off
On
Com
Off
Fault
N/O
Com
N/C
Gnd
In
Sequential Turn-On
Input
V-In
3.3V
Out