Rotel Power Supply RB 951 MkII User Guide

Owner’s Manual  
RB-951 MkII  
Stereo Power Amplifier  
POWER AMPLIFIER RB-951 MkII  
CH1  
CH2  
PROTECTION  
CLIPPING  
POWER  
BRIDGED  
MONO  
LEVEL  
LEVEL  
 
3
2: Hookup (Stereo or Parallel Mono modes)  
RCA OUTPUTS  
L
R
12 TRIG IN  
SIGNAL SENSE  
CAUTION  
RISK OF ELECTRIC SHOCK  
DO NOT OPEN  
10 A  
OFF AC BREAKER  
AVIS: RISQUE DE CHOC ELECTRIQUE–NE PAS OUVRIR  
SPEAKERS  
BRIDGED  
CHANNEL 2  
CHANNEL 1  
INPUT  
CH2 CH1  
WARNING:  
TO REDUCE THE RISK  
OF FIRE OR ELECTRICAL  
SHOCK, DO NOT EXPOSE  
THIS EQUIPMENT TO RAIN  
OR MOISTURE.  
CH2  
CH1  
POWER AMPLIFIER  
MODEL NO. RB-951 MkII  
POWER CONSUMPTION: 200W  
BRIDGED  
MONO  
NORMAL  
STERO  
SIGNAL OUTPUT  
LINK  
RB-951 MkII  
 
RB-951 MkII Stereo Power Amplifier  
4
3: Hookup (Bridged Mono mode)  
RCA OUTPUTS  
L
R
12 TRIG IN  
SIGNAL SENSE  
CAUTION  
RISK OF ELECTRIC SHOCK  
DO NOT OPEN  
10 A  
OFF AC BREAKER  
AVIS: RISQUE DE CHOC ELECTRIQUE–NE PAS OUVRIR  
SPEAKERS  
BRIDGED  
CHANNEL 2  
CHANNEL 1  
INPUT  
WARNING:  
TO REDUCE THE RISK  
CH2  
CH1  
CH2  
CH1  
OF FIRE OR ELECTRICAL  
SHOCK, DO NOT EXPOSE  
THIS EQUIPMENT TO RAIN  
OR MOISTURE.  
POWER AMPLIFIER  
MODEL NO. RB-951 MkII  
POWER CONSUMPTION: 200W  
BRIDGED  
MONO  
NORMAL  
STERO  
SIGNAL OUTPUT  
LINK  
RB-951 MkII  
12 TRIG IN  
SIGNAL SENSE  
CAUTION  
RISK OF ELECTRIC SHOCK  
DO NOT OPEN  
10 A  
AVIS: RISQUE DE CHOC ELECTRIQUE–NE PAS OUVRIR  
SPEAKERS  
BRIDGED  
OFF AC BREAKER  
CHANNEL 2  
CHANNEL 1  
INPUT  
CH2 CH1  
WARNING:  
TO REDUCE THE RISK  
OF FIRE OR ELECTRICAL  
SHOCK, DO NOT EXPOSE  
THIS EQUIPMENT TO RAIN  
OR MOISTURE.  
CH2  
CH1  
POWER AMPLIFIER  
MODEL NO. RB-951 MkII  
POWER CONSUMPTION: 200W  
BRIDGED  
MONO  
NORMAL  
STERO  
SIGNAL OUTPUT  
LINK  
RB-951 MkII  
 
5
English  
WARNING: There are no user serviceable parts inside.  
Refer all servicing to qualified service personnel.  
WARNING: To reduce the risk of fire or electric shock,  
do not expose the unit to moisture or water. Do not  
allow foreign objects to get into the enclosure. If the  
unit is exposed to moisture, or a foreign object gets  
into the enclosure, immediately disconnect the power  
cord from the wall. Take the unit to a qualified service  
person for inspection and necessary repairs.  
Read all the instructions before connecting or operating the com-  
ponent. Keep this manual so you can refer to these safety in-  
structions.  
Heed all warnings and safety information in these instructions  
and on the product itself. Follow all operating instructions.  
Clean the enclosure only with a dry cloth or a vacuum cleaner.  
You must allow 10 cm or 4 inches of unobstructed clearance around  
the unit. Do not place the unit on a bed, sofa, rug, or similar sur-  
face that could block the ventilation slots. If the component is placed  
in a bookcase or cabinet, there must be ventilation of the cabinet  
to allow proper cooling.  
Keep the component away from radiators, heat registers, stoves,  
or any other appliance that produces heat.  
The unit must be connected to a power supply only of the type  
and voltage specified on the rear panel of the unit.  
Connect the component to the power outlet only with the sup-  
plied power supply cable or an exact equivalent. Do not modify  
the supplied cable in any way. Do not attempt to defeat ground-  
ing and/or polarization provisions. Do not use extension cords.  
Do not route the power cord where it will be crushed, pinched,  
bent at severe angles, exposed to heat, or damaged in any way.  
Pay particular attention to the power cord at the plug and where  
it exits the back of the unit.  
The power cord should be unplugged from the wall outlet if the  
unit is to be left unused for a long period of time.  
Immediately stop using the component and have it inspected and/  
or serviced by a qualified service agency if:  
The power supply cord or plug has been damaged.  
Objects have fallen or liquid has been spilled into the unit.  
The unit has been exposed to rain.  
The unit shows signs of improper operation  
The unit has been dropped or damaged in any way  
Place the unit on a fixed, level surface strong enough to support  
its weight. Do not place it on a moveable cart that could tip over.  
 
RB-951 MkII Stereo Power Amplifier  
6
Speakers................................................9  
Contents  
1: Controls, Connections, & Internal Jumpers  
2: Hookup (Stereo or Parallel Mono modes)  
3: Hookup (Bridged Mono mode)  
About Rotel  
Speaker Selection  
9
9
9
9
2
3
4
A family whose passionate interest in music  
led them to manufacture high fidelity compo-  
nents of uncompromising quality founded Rotel  
over 30 years ago. Over the years that pas-  
sion has remained undiminished and the goal  
of providing exceptional value for audiophiles  
and music lovers regardless of their budget,  
is shared by all Rotel employees.  
Speaker Wire Selection  
Polarity and Phasing  
Speaker Connections  
About Rotel ...........................................6  
Getting Started ......................................7  
Internal Jumper Settings  
for Custom Installation .........................10  
Bypassing the Variable Level Controls  
Operating Features  
A Few Precautions  
Placement  
7
7
7
The engineers work as a close team, listen-  
ing to, and fine tuning each new product until  
it reaches their exacting musical standards.  
They are free to choose components from  
around the world in order to make that prod-  
uct the best they can. You are likely to find ca-  
pacitors from the United Kingdom and Ger-  
many, semiconductors from Japan or the United  
States, and toroidal power transformers manu-  
factured in Rotel’s own factory.  
(S603 and S604)  
10  
10  
10  
Input Sensitivity  
(S605 and S606)  
AC Power and Control ............................7  
Selecting Parallel Mono Mode  
(S602 and P1/P3)  
AC Power Input  
7
7
7
8
8
8
Troubleshooting ....................................10  
Power Switch and Indicator  
Auto Turn On/Off Mode Selector  
12V Trigger Input  
Front Panel Power Indicator Is Not Lit  
No Sound  
10  
10  
10  
Rotel’s reputation for excellence has been  
earned through hundreds of good reviews and  
awards from the most respected reviewers in  
the industry, who listen to music every day.  
Their comments keep the company true to its  
goal – the pursuit of equipment that is musi-  
cal, reliable and affordable.  
Protection Indicator Is Lit  
Circuit Breaker  
Protection Indicators  
Specifications .......................................11  
Stereo/Mono Mode Selection .................8  
Bridge Switch and  
Front Panel Bridge LED  
Signal Connections..................................8  
8
All of us at Rotel thank you for buying this  
product and hope it will bring you many hours  
of enjoyment.  
RCA Inputs  
8
8
9
9
Input Level Controls  
Clipping Indicators  
Signal Output Link  
 
7
English  
Placement  
Power Switch and Indicator  
Getting Started  
Thank you for purchasing the Rotel RB-951MkII  
Stereo Power Amplifier. When used in a high-  
quality music or home theater system, your Rotel  
amplifier will provide years of musical enjoy-  
ment.  
The RB-951MkII generates heat as part of its  
normal operation. The heat sinks and ventila-  
tion openings in the amplifier are designed  
to dissipate this heat. The ventilation slots in  
the top cover must be unobstructed. There  
should be 10 cm (4 inches) of clearance around  
the chassis, and reasonable airflow through  
the installation location, to prevent the ampli-  
fier from overheating.  
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 automatic  
power-on modes), push the switch in. The LED  
indicator above the switch will light, indicat-  
ing that the amplifier is turned on. To turn the  
amplifier off, push the button again and re-  
turn it to the out position.  
The RB-951MkII is a sophisticated two-chan-  
nel power amplifier. Discrete output devices,  
a massive power supply with toroidal trans-  
former, premium components, and Rotel’s Bal-  
anced Design ensure superb sound quality.  
High current capability allows the RB-951MkII  
to drive difficult speaker loads with ease.  
Auto Turn On/Off Mode  
Selector  
Likewise, remember the weight of the ampli-  
fier when you select an installation location.  
Make sure that the shelf or cabinet can sup-  
port its considerable bulk. Again, use common  
sense.  
The RB-951MkII provides three different options  
for manual or automatic power on/off opera-  
tion. These modes are selectable using a three-  
position slide switch on the back panel as  
follows:  
Operating Features  
• Two-channel Stereo or Bridged Mono op-  
eration (back panel switchable)  
AC Power and Control  
With the switch in the OFF position,  
the amplifier is turned on or off manually  
using the front panel power switch. Also  
use this mode if you are using a switched  
AC outlet to control power to the ampli-  
fier.  
• Optional Parallel Mono operation for driv-  
ing low impedance multi-speaker loads in  
custom installation applications (requires  
resetting internal jumpers).  
AC Power Input  
The RB-951MkII is supplied with the proper AC  
power chord. Use only this cord or an exact  
equivalent. Do not use an extension cord. A  
heavy duty multi-tap power outlet strip may  
be used, but only if it is rated to handle the  
current demanded by the RB-951MkII.  
• User-selectable power on/off configuration:  
manual, automatic signal sensing, or con-  
trolled by remote 12 volt trigger signal.  
With the switch in the SIGNAL SENS-  
ING position, the amplifier turns on au-  
tomatically when a signal is sensed at the  
inputs. The amplifier will go into standby  
mode five minutes after no signal is 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.  
• Front panel input level controls  
Be sure the power switch on the front panel  
of the RB-951MkII 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.  
• Protection circuitry with front panel indi-  
cators  
• Front panel clipping indicators  
A Few Precautions  
Your RB-951MkII is configured at the factory  
for the proper AC line voltage in the country  
where you purchased it (USA: 115 volts/60  
Hz , Europe: 230 volts/50 Hz). The AC line  
configuration is noted on a label on the back  
panel.  
Please read this manual carefully. In addition  
to basic installation and operating instructions,  
it provides valuable information on various  
RB-951MkII system configurations as well as  
general information that will help you get op-  
timum performance from your system. Please  
contact your authorized Rotel dealer for an-  
swers to any questions you might have. In ad-  
dition, all of us at Rotel welcome your ques-  
tions and comments.  
With the switch in the +12V TRIG.  
IN position, the amplifier is turned on  
automatically when a 12 volt trigger sig-  
nal is present at the screw terminals adja-  
cent to the left of the switch. The amplifier  
will go into standby mode if the +12 volt  
signal is not present. The front panel  
POWER SWITCH overrides this function.  
It must be ON for the +12V trigger to work.  
Turning the switch OFF cuts power to the  
amplifier, regardless of whether or not a  
trigger signal is present.  
NOTE: Should you move your RB-951MkII to  
another country, it is possible to configure your  
amplifier for use on a different line voltage.  
Do not attempt to perform this conversion your-  
self. Opening the enclosure of the RB-951MkII  
exposes you to dangerous voltages. Consult  
a qualified technician or the Rotel factory ser-  
vice department for information.  
Save the RB-951MkII shipping carton and all  
enclosed packing material for future use. Ship-  
ping or moving the RB-951MkII in anything other  
than the original packing material may result  
in severe damage to your amplifier.  
If you are going to be away from home for  
an extended period of time, it is a sensible  
precaution to unplug your amplifier.  
Be sure to keep the original sales receipt. It is  
your best record of the date of purchase, which  
you will need in the event warranty service is  
ever required.  
 
RB-951 MkII Stereo Power Amplifier  
8
12V Trigger Input  
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.  
Signal Connections  
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 RB-951MkII 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.  
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.  
Stereo/Mono Mode  
Selection  
The RB-951MkII provides three options for  
Stereo or Bridged Mono operation.  
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.  
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.  
Stereo mode: Conventional 2-channel  
stereo operation. Minimum speaker load:  
4 ohms.  
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.  
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.  
Protection Indicators  
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.  
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.  
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.  
For Parallel Mono operation, either in-  
put may be used. The signal from either will  
be sent to all speaker outputs.  
In addition, the RB-951MkII includes 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.  
Input Level Controls  
Bridge Switch  
Panel Bridge LED  
and Front  
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 CH1 level control  
changes the gain of the left channel; the CH2  
level control changes the right channel.  
A rear panel switch selects Stereo mode or  
Bridged Mono mode.  
Should a faulty condition arise, the amplifier  
will stop playing and the PROTECTION LEDS  
on the front panel will light.  
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.  
To adjust these controls, use a small, flat-blade  
screwdriver. Turn the control clockwise to in-  
crease gain. Turn counterclockwise to reduce  
gain.  
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.  
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.  
NOTE: These controls may be disabled by re-  
setting an internal jumper.  
 
9
English  
Clipping Indicators  
Speaker Wire Selection  
If you are using banana plugs, connect them  
to the wires and then plug into the backs of  
the speaker connectors. The collars of the  
speaker connectors should be screwed in all  
the way (clockwise).  
Two front panel LEDs (one for each channel)  
flash to indicate when the amplifier is “clip-  
ping” or being asked to deliver more output  
current than it is capable of delivering. Clip-  
ping will cause distortion levels to increase.  
Use insulated two-conductor stranded wire to  
connect the RB-951MkII to the speakers. The  
size and quality of the wire can have an au-  
dible effect on the performance of the system.  
Standard speaker wire will work, but can re-  
sult in lower output or diminished bass response,  
particularly over longer distances. In general,  
heavier wire will improve the sound. For best  
performance, you may want to consider spe-  
cial high-quality speaker cables. Your autho-  
rized Rotel dealer can help in the selection of  
appropriate cables for your system.  
If you are using terminal lugs, connect them  
to the wires. If you are attaching bare wires  
directly to the speaker connectors, separate  
the wire conductors and strip back the insu-  
lation from the end of each conductor. Be careful  
not to cut into the wire strands. Unscrew (turn  
counterclockwise) the speaker connector col-  
lar. Place the connector lug around the shaft,  
or insert the bundled wire into the hole in the  
shaft. Turn the collars clockwise to clamp the  
connector lug or wire firmly in place.  
Occasional brief clipping on the loudest mu-  
sical passages is acceptable. However, sus-  
tained or frequent clipping is one of the most  
common causes of speaker damage and should  
be avoided.  
Should this occur, either reduce the overall gain  
of the system by turning down the master volume  
control on your preamp. Alternatively, you may  
wish to permanently reduce the gain of the  
amplifier using the front panel level controls  
(see previous section).  
Polarity and Phasing  
The polarity – the positive/negative orienta-  
tion of the connections – for every speaker and  
amplifier connection must be consistent so all  
the speakers will be in phase. If the polarity  
of one connection is mistakenly reversed, bass  
output will be very weak and stereo imaging  
degraded. All wire is marked so you can iden-  
tify the two conductors. There may be ribs or  
a stripe on the insulation of one conductor.  
The wire may have clear insulation with dif-  
ferent color conductors (copper and silver).  
There may be polarity indications printed on  
the insulation. Identify the positive and nega-  
tive conductors and be consistent with every  
speaker and amplifier connection.  
NOTE: Be sure there are no loose wire strands  
that could touch adjacent wires or connec-  
tors.  
Signal Output Link  
This pair of RCA connections can be used to  
pass the unprocessed input signals to another  
audio component, for example to “daisy-chain”  
an additional amplifier to drive a second set  
of speakers. Any INPUT SIGNAL is also avail-  
able at these LINK outputs.  
In Stereo mode: Connect the left speaker  
to the pair of speaker connectors labeled CH1.  
Connect the right speaker to the speaker con-  
nectors labeled CH2. Follow the labels printed  
above the connectors and make sure the  
BRIDGE MODE switch is set to the NORMAL  
STEREO position. (See Figure 2)  
In Bridged Mono mode: Connect the posi-  
tive terminal of the speaker to the speaker con-  
nector labeled BRIDGE +. Connect the nega-  
tive terminal of the speaker to the speaker con-  
nector labeled BRIDGE –. Follow the labels  
printed below the connectors and make sure  
the BRIDGE switch is set to the BRIDGE MONO  
position. (See Figure 3)  
Speakers  
The RB-951MkII has two pair of speaker con-  
nectors, one pair for each channel. These can  
be used to connect two loudspeakers in Ste-  
reo mode, or to connect one loudspeaker in  
Bridged Mono mode.  
Speaker Connections  
See Figures 2 & 3  
The RB-951MkII has one pair of color coded  
connections per channel. Labels above the  
connectors show the proper connections for  
Stereo mode. Labels below show the proper  
connections for Bridged Mono mode.  
Speaker Selection  
In Parallel Mono mode: Connect the speak-  
ers in the same fashion as in the Stereo mode.  
You can use the connectors for either chan-  
nel or both – the same output signal is present  
at both pair of connectors. (See Figure 2)  
The nominal impedance of the loudspeaker(s)  
connected to the RB-951MkII in the various  
operating modes should be:  
These speaker connectors accept bare wire,  
connector lugs, or “banana” type connectors  
(except in the European Community countries  
where their use is not permitted).  
Stereo mode: minimum 4 ohms  
Bridged Mono mode:minimum 8 ohms  
• Parallel Mono mode: minimum 2 ohms  
Route the wires from the RB-951MkII to the  
speakers. Give yourself enough slack so you  
can move the components enough to allow  
access to the speaker connectors.  
When driving multiple pairs of speakers con-  
nected in parallel, the effective impedance the  
amplifier sees is cut in half. For example, when  
driving two pair of 8 ohm speakers, the am-  
plifier sees a 4 ohm load. When driving mul-  
tiple speakers in parallel, select speakers with  
a nominal impedance of 8 ohms or higher.  
 
RB-951 MkII Stereo Power Amplifier  
10  
Input Sensitivity  
(S605 and S606)  
Internal Jumper Settings  
for Custom Installation  
(see figure 1)  
Troubleshooting  
Jumper blocks S605 and S606 are used to  
set the input sensitivity of the amplifier.  
Most difficulties in audio systems are the re-  
sult of poor or wrong connections, or improper  
control settings. If you encounter problems,  
isolate the area of the difficulty, check the control  
settings, determine the cause of the fault and  
make the necessary changes. If you are un-  
able to get sound from the RB-951MkII, refer  
to the suggestions for the following conditions:  
For high sensitivity (0.775v input for  
rated power): place the jumpers across pins  
1 and 2 on jumper blocks S605 and S606.  
There are internal jumpers that can be used  
to disable the front panel level controls, to select  
one of two input sensitivity settings, and to  
engage the special Parallel Mono mode for  
driving low impedance speaker combinations  
in custom installations.  
For low sensitivity (1.5v input for rated  
power): place the jumpers across pins 2 and  
3 on jumper blocks S605 and S606.  
Front Panel Power Indicator Is  
Not Lit  
Selecting Parallel Mono Mode  
(S602 and P1/P3)  
WARNING: Removing the top cover of the am-  
plifier to access the jumpers may expose you  
to potentially dangerous voltages. These set-  
tings should only be made by a qualified tech-  
nician. The AC power cord must be removed  
from the amplifier before the top cover is re-  
moved.  
No main power to the RB-951MkII. Check AC  
power connections at the amplifier and the  
AC outlet. Check the front panel power switch.  
Make sure that it is set to the ON position. If  
using signal sensing auto power-on, make sure  
that a signal is present at the inputs. If using  
12V trigger power-on, make sure that a trig-  
ger signal is present at rear panel screw ter-  
minals.  
As described earlier in this manual, the two  
most common operating configurations for the  
RB-951MkII (Stereo mode and Bridged Mono  
mode) are selectable with a back panel switch  
and require no internal changes.  
After removing the top cover, the jumper blocks  
can be found on the circuit board as shown  
in Figure 1. Each jumper block has a printed  
identification number. The function, ID num-  
bers, and settings for each jumper block are  
provided below. To change the setting, place  
the jumper on the appropriate pins as indi-  
cated.  
The third configuration, Parallel Mono mode,  
allows both channels of the amplifier to be com-  
bined in parallel. This mode is useful for driv-  
ing a low impedance speaker load such as  
driving multiple speakers in a custom instal-  
lation.  
No Sound  
If the amp is getting AC power, but is producing  
no sound, check the PROTECTION INDICA-  
TORS on the front panel. If lit, see below. If  
not, check all of your connections and con-  
trol settings on associated components. Make  
sure that your input connections and speaker  
connections match your selected stereo/mono  
configuration.  
This Parallel Mono mode can be selected only  
by setting internal jumpers (jumper block S602)  
and changing a buss wire connection (con-  
nectors P1and P2).  
Bypassing the Variable Level  
Controls (S603 and S604)  
NOTE: it is essential that Parallel Mono mode  
not be engaged at the same time as Stereo  
mode. This will blow the internal rail fuses.  
Make sure that you follow all of the instruc-  
tions below carefully.  
The front panel Level Controls allow you to  
adjust the input gain for each channel of the  
amplifier. These level controls can by bypassed  
by changing the jumper position on jumper  
blocks S603 (for CH 1) and S604 (for CH2).  
Protection Indicator Is Lit  
The front panel PROTECTION INDICATORS  
light when the RB-951MkII protection circuits  
have shut off the amplifier. Typically, this oc-  
curs only when the ventilation openings are  
blocked, when there is faulty speaker wiring,  
or after a period of extreme use. Turn off the  
system and wait for the amp to cool. Then push  
the front panel power switch in and out to re-  
set the protection devices. If the problem is not  
corrected or reoccurs, there is a problem with  
the system or the amplifier itself.  
To disable the variable level controls:  
place a jumper across pins 2 and 3 on jumper  
block S603 and across pins 1 and 2 on jumper  
block S604.  
To convert to Parallel Mono mode:  
1. Place the jumper across pins 1 and 2 on  
jumper block S602.  
2. Locate the buss wire linking the P2 connector  
to the P3 connector. Remove the wire from  
P3 and move it to the adjacent P1 connector.  
For Parallel Mono mode, the buss wire must  
link P2 to P1.  
To enable the variable level controls:  
place a jumper across pins 1 and 2 on jumper  
block S603 and across pins 2 and 3 on jumper  
block S604.  
To return to normal configuration (Ste-  
reo or Bridged Mono modes):  
1. Place the jumper across pins 2 and 3 on  
jumper block S602.  
2. Locate the buss wire linking the P2 connector  
to the P1 connector. Remove the wire from  
P1 and move it to the adjacent P3 connector.  
For normal mode, the buss wire must link  
P2 to P3.  
 
11  
English  
Specifications  
Continuous Power Output Stereo Mode  
(20-20 kHz, < 0.03% THD)  
50 watts/ch into 8 ohms  
Continuous Power Output Bridged Mono  
Mode (20-20 kHz, < 0.1% THD)  
150 watts/ch into 8 ohms  
Total Harmonic Distortion  
(20Hz-20kHz, 8 ohms)  
< 0.03%  
Intermodulation Distortion  
(60 Hz : 7 kHz, 4:1)  
< 0.03%  
Frequency Response ( 1 dB)  
15Hz-100kHz  
Damping Factor (20-20,000 Hz, 8 ohms)  
280  
Speaker Impedance (combined load)  
Stereo mode: 4 ohms minimum  
Bridged Mono mode: 8 ohms minimum  
Parallel Mono mode: 2 ohms minimum  
Signal to Noise Ratio (IHF A network)  
116 dB  
Input Impedance  
32 k Ohms  
Input Sensitivity  
1.5 volt (low setting)  
0.775 volt (high setting)  
Auto Turn On Threshold Level (if activated)  
10 mV input signal  
Auto Turn Off Delay Time (if activated)  
5 minutes with no signal  
Power Requirements  
USA: 115 Volts, 60 Hz  
Europe: 230 Volts, 50 Hz  
Power Consumption  
200 Watts  
Dimensions (W x H x D)  
440 x 92 x 334 mm  
173/8 x 35/8 x 131/4 in  
Weight (net)  
6.8 kg, 15 lb.  
All specifications are accurate at the time of printing.  
Rotel reserves the right to make improvements  
without notice.  
 
The Rotel Co. Ltd.  
10-10 Shinsen-Cho  
Shibuya-Ku  
Tokyo 150-0045  
Japan  
Phone: +81 3-5458-5325  
Fax: +81 3-5458-5310  
Rotel of America  
54 Concord Street  
North Reading, MA 01864-2699  
USA  
Phone: +1 978-664-3820  
Fax: +1 978-664-4109  
Rotel Europe  
Meadow Road  
Worthing, West Sussex BN11 2RX  
England  
Phone: +44 (0)1903 524 813  
Fax: +44 (0)1903 524 831  
Rotel Deutschland  
Kleine Heide 12  
D-33790 Halle/Westf.  
Germany  
Phone: +49 05201-87170  
Fax: +49 05201-73370  
082 OMRB-951MkII 113099  
 

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