Rotel RB-951MkII Stereo/Mono Mode Selection, Signal Connections, 12V Trigger Input, RCA Inputs

RB-951 MkII Stereo Power Amplifier 8

12V Trigger Input

A pair of screw terminals for connecting the wires carrying a +12 volt trigger signal to turn the amplifier on and off, such as might be used in an elaborate custom installation. To use this feature the adjacent slide switch must be placed to the left position (see previous section).

The TRIGGER INPUT accepts any control sig- nal (AC or DC) ranging from 3 volts to 30 volts. The screw terminals are labeled “+ and –” Observe proper polarity when connecting the trigger signal wiring.

Circuit Breaker

A 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 excessive current draw. To reset the circuit breaker, press the button. Should it repeatedly open, contact your authorized Rotel dealer for troubleshooting assistance.

Protection Indicators

A thermal protection circuit protects the am- plifier against potential damage in the event of extreme or faulty operating conditions. Unlike many designs, the RB-951MkII’s protection cir- cuit is independent of the audio signal and has no impact on sonic performance. Instead, the protection circuit monitors the temperature of the output devices and shuts down the am- plifier if temperatures exceed safe limits.

In addition, the RB-951MkIIincludes overcurrent protection which operates only when load im- pedances drops too low. This protection is in- dependent for the left and right channels with separate front panel PROTECTION LEDS for each.

Should a faulty condition arise, the amplifier will stop playing and the PROTECTION LEDS on the front panel will light.

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

In most cases, the protection circuitry activates because of a fault condition such as shorted speaker wires, or inadequate ventilation lead- ing to an overheating condition. In very rare cases, highly reactive or extremely low imped- ance speaker loads could cause the protec- tion circuit to engage.

Stereo/Mono Mode

Selection

The RB-951MkIIprovides three options for Stereo or Bridged Mono operation.

•Stereo mode: Conventional 2-channel stereo operation. Minimum speaker load: 4 ohms.

•Bridged Mono mode: Serial bridged mode which more than doubles the am- plifier power into a single speaker. Mini- mum speaker load: 8 ohms.

•Parallel Mono mode: A special bridge mode that allows the amplifier to drive extremely low impedance speaker loads such as might be encountered driving mul- tiple speakers in a custom installation. Minimum speaker load: 2 ohms.

The first two modes are selected using a rear panel switch. The Parallel Mono mode requires setting internal jumpers and should only be done by a qualified technician. See the IN- TERNAL JUMPER SETTINGS section at the end of this manual.

Bridge Switch and Front Panel Bridge LED

A rear panel switch selects Stereo mode or Bridged Mono mode.

For Stereo mode: Slide the switch to the right, use both input connectors, and connect one speaker to each pair of speaker connectors. The front panel LED will be extinguished.

For Bridged Mono mode: Slide the switch to the left, use only the CH1 INPUT connec- tion, and connect only one speaker to the two outer speaker connectors. The front panel LED will light to indicate Bridged Mono mode.

Signal Connections

The RB-951MkIIprovides 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 Figures 2 and 3

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

For Stereo operation, use both inputs. Con- nect the left channel output of your preamp to the CH 1 INPUT on the RB-951MkII. Con- nect the right channel of your preamp to the CH 2 INPUT. Make sure that the BRIDGE SWITCH is in the NORMAL STEREO position.

For Bridged Mono operation, use only the CH1 INPUT. Connect one output channel of your preamp to the CH 1 INPUT on the RB-951MkII. Connect the other channel of your preamp to a second amplifier. Make sure that the BRIDGE SWITCH selector switch is in the BRIDGED MONO position.

For Parallel Mono operation, either in- put may be used. The signal from either will be sent to all speaker outputs.

Input Level Controls

Two recessed controls on the front panel, one for each channel, provide input level adjust- ments. These allow you to adjust the gain of the amplifier to match other components in an elaborate system. The CH 1 level control changes the gain of the left channel; the CH 2 level control changes the right channel.

To adjust these controls, use a small, flat-blade screwdriver. Turn the control clockwise to in- crease gain. Turn counterclockwise to reduce gain.

NOTE: These controls may be disabled by re- setting an internal jumper.