Signal Connections

RKB-250Power Ampliﬁer

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.

•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.

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.