Signal connections, Ac power and control – ROTEL RKB-250 User Manual

Page 12

RKB-250 Power Ampliﬁer

• With the switch in the SIGNAL SENSE po-

sition, the ampliﬁer turns on automatically
when a signal is detected at the inputs.
The ampliﬁer will go into standby mode
several minutes after no signal is no lon-
ger present. The front panel power switch
overrides this function. It must be ON for
the signal sensing to work. Turning the
switch OFF cuts power to the ampliﬁer,
regardless of whether or not a signal is
present.

• With the switch in the 12V TRIG position,

the ampliﬁer is turned on automatically
when a 12 volt trigger signal is present
at the 12V TRIG input to the left of the
switch. The ampliﬁer goes into standby
mode if the +12 volt signal is not present.
The front panel POWER SWITCH over-
rides this function. It must be ON for the
+12V trigger to work. Turning the switch
OFF cuts power to the ampliﬁer, regard-
less of whether or not a trigger signal is
present.

12V Trigger Input

An input jack for connecting the wires car-
rying a +12 volt trigger signal from a Rotel
preamp or surround sound processor to turn
the ampliﬁer on and off. To use this feature
the adjacent slide switch must be placed to
the left position (see previous section).

The TRIGGER INPUT accepts any control
signal (AC or DC) ranging from 3 volts to
30 volts. Using a cable with mono 3.5 mm
mini-plugs on both ends. The +12 V DC sig-
nal appears at the “tip” connector.

12V Trigger Output

The 12V TRIG jack labeled OUT is used to
pass the remote turn-on signal to a second
Rotel ampliﬁer. Any 12V Trigger signal at
the INPUT jack will be passed through to
the OUT jack.

Circuit Breaker

A 10 amp circuit breaker on the rear panel
protects the ampliﬁer’s electrical circuity.
Generally, the circuit breaker will only open
under a fault condition which results in exces-
sive current draw. To reset the circuit breaker,
press the button. Should it repeatedly open,
contact your authorized Rotel dealer for trou-
bleshooting assistance.

Protection Indicators

A thermal protection circuit protects the am-
pliﬁer against potential damage in the event
of extreme or faulty operating conditions. Un-
like many designs, the RKB-250’s protection
circuit is independent of the audio signal and
has no impact on sonic performance. Instead,
the protection circuit monitors the tempera-
ture of the output devices and shuts down the
ampliﬁer if temperatures exceed safe limits.

In addition, the RKB-250 includes overcurrent
protection which operates only when load
impedance drops too low.

Should a faulty condition arise, the ampli-
ﬁer will stop playing and one or both of the
PROTECTION LEDS on the front panel will
light indicating a fault with the left and/or
right channels.

If this happens, turn the ampliﬁer off, let it
cool down for several minutes, and attempt
to identify and correct the problem. When
you turn the ampliﬁer back on, the protec-
tion circuit will automatically reset and the
PROTECTION LEDS should go out.

In most cases, the protection circuitry acti-
vates because of a fault condition such as
shorted speaker wires, or inadequate ventila-
tion leading to an overheating condition. In
very rare cases, highly reactive or extremely
low impedance speaker loads could cause
the protection circuit to engage.

Signal Connections

The RKB-250 provides standard conventional
input connections — unbalanced RCA type
connections as found on nearly all audio
equipment. In addition, there is a pair of SIG-
NAL OUTPUT LINK connections for passing
the unchanged input signal on to another
audio component.

RCA Inputs

See Figure 2

These RCA inputs accept audio signals from
preampliﬁers or surround sound processors.
Use high quality audio interconnect cables
for best performance.

Connect the left channel output of your pre-
amp to the LEFT INPUT on the RKB-250. Con-
nect the right channel of your preamp to the
RIGHT INPUT.

AC Power and Control

AC Power Input

Your RKB-250 is conﬁgured at the factory
for the proper AC line voltage in the country
where you purchased it (USA: 120 volts/60
Hz, Europe: 230 volts/50 Hz). The AC line
configuration is noted on a label on the
back panel.

The RKB-250 is supplied with the proper AC
power cord. Use only this cord or an exact
equivalent. Do not modify the supplied cord.
Do not use an extension cord.

Be sure the power switch on the front panel
of the RKB-250 is turned off. Then, plug one
end of the cord into the AC power connector
on the back panel of the ampliﬁer. Plug the
other end into an appropriate AC outlet.

If you are going to be away from home for
an extended period of time, it is a sensible
precaution to unplug your ampliﬁer.

Power Switch

Indicator LED

The power switch is located on the left side
of the front panel. To turn the ampliﬁer on
(or to activate either of the optional auto-
matic power-on modes), push the switch in.
The LED indicator above the switch will light,
indicating that the ampliﬁer is turned on. To
turn the ampliﬁer off, push the button again
and return it to the out position.

Auto Turn On/Off Mode Selec-

tor

The RKB-250

provides three different op-

tions for manual or automatic power on/off
operation. These modes are selectable us-
ing a three-position slide switch on the back
panel as follows:

• With the switch in the OFF position, the

ampliﬁer is turned on or off manually us-
ing the front panel power switch. Also use
this mode if you are using a switched AC
outlet to control power to the ampliﬁer.