Bogen Stereo Amplifier CAM2 User Manual

CAM2 Mixer/Pre-Amplifier  
Installation and Use Manual  
© 2001 Bogen Communications, Inc.  
All rights reserved. Specifications subject to change.  
54-2039-01R2 Printed in Korea. 0112  
 
Contents  
Page  
INTRODUCTION & INSTALLATION ..........................................................................................3  
Introduction ..........................................................................................................................................................3  
Installation..............................................................................................................................................................3  
PANEL DESCRIPTIONS ..................................................................................................................4  
Front Panel ............................................................................................................................................................4  
Rear Panel..............................................................................................................................................................4  
INPUT CONNECTIONS ..............................................................................................................5-6  
Microphone Inputs ..............................................................................................................................................5  
Phantom Power....................................................................................................................................................5  
Microphone Cable Wiring..................................................................................................................................6  
AUX IN ..................................................................................................................................................................6  
OUTPUT CONNECTIONS..........................................................................................................7-8  
BAL/OUT to Balanced Input of Other Equipment......................................................................................7  
BAL/OUT to Microphone Input of Other Equipment................................................................................7  
LINE OUT..............................................................................................................................................................8  
BRIDGING MIXERS..........................................................................................................................9  
Bridging Connections..........................................................................................................................................9  
OPERATION....................................................................................................................................10  
Power ..................................................................................................................................................................10  
MIC Gain Control..............................................................................................................................................10  
AUX Gain Control............................................................................................................................................10  
Clip Indicator......................................................................................................................................................10  
Master Gain Control ........................................................................................................................................10  
Output Level Meter..........................................................................................................................................10  
AUDIO SYSTEM LEVEL ................................................................................................................11  
Setting System Levels........................................................................................................................................11  
SPECIFICATIONS ..........................................................................................................................12  
LIMITED WARRANTY ..................................................................................................................13  
 
Introduction & Installation  
Introduction  
The Bogen Model CAM2 is a mixer/pre-amplifier that provides four MIC inputs and one AUX input while supply-  
ing both MIC and high level outputs. The CAM2 is particularly well-suited for expanding the number of inputs of  
Bogen public address amplifiers.  
The CAM2 accommodates low-impedance microphones and has an input for tuners or other high level sources.  
Outputs are provided for high-impedance unbalanced and low-impedance balanced MIC inputs and line level inputs  
to a public address amplifier,tape deck or similar equipment.Units may be interconnected to provide a greater num-  
ber of inputs.  
The CAM2 operates from a 120V AC, 60Hz source. It may be mounted in a standard 19" equipment rack using a  
Bogen Model RPK35B rack mounting kit or in a wall with a Bogen Model WMK1 in-wall mounting kit.  
Caution:To reduce the risk of fire or electric shock, do not expose this unit to rain or excessive moisture.  
Unpacking  
Your unit was carefully checked before leaving the factory. Inspect the shipping container and the unit carefully for  
indications of improper handling. If the unit has been damaged, make an immediate claim to the distributor from  
whom it was purchased. If it was shipped to you, notify the transportation company and place a claim.  
Power & Grounding  
The AC line cord has a three-prong plug that should be plugged into a three-wire, grounded 120V AC, 60Hz out-  
let. If a three-wire outlet is not available, then use an adapter and secure the pigtail lead to the grounded wall plate  
mounting screw. It is important to ground the unit. If the wall plate screw is not grounded, connect the wire from  
the GND terminal of the mixer/pre-amplifier to a suitable earth ground.  
Installation  
Rack Mounting  
Bogen Model RPK35B Rack Panel Kit is designed to mount the CAM2 in a standard 19" sound equipment rack. The  
panel is fabricated from cold-rolled steel and finished in black enamel.  
In-Wall Mounting  
Bogen Model WMK1 is designed to mount the mixer/pre-amplifier flush in a wall. Depth of the mounted unit is  
3-1/2".  
3
 
Panel Descriptions  
Front Panel  
1. Input OverVoltage LEDs (Clipping LED) - LED will light when input is overdriven.  
2. MIC Channel Gain Controls - Controls the gain levels of the MIC channels.  
3. AUX Gain Control - Controls the gain level of the AUX input.  
4. Output Meter - LED meter indicates peak output signal level.  
5. Master Gain Control - Adjusts the overall output level.  
6. Power Switch & Power Indicator - Power switch will illuminate when Power Switch is turned "ON".  
Rear Panel  
1. Power Connection - 120V AC, 60Hz, .043A.  
2. Output XLR Connector - Provides a balanced output compatible with most professional audio equipment.  
3. Output Level Switch - Switch changes the nominal signal level of the XLR output from +4dB to -50dB.  
4. Line Output Connector (Line Out) - RCA jack provides output signal levels compatible with most amplifiers,  
recording equipment, and other audio equipment. Not affected by Output Level switch.  
5. Bridging - The bridging jacks facilitate the connecting together of mixers to obtain additional inputs without using any  
of the CAM2 inputs.  
6. Auxiliary Input (AUX In) - A dedicated unbalanced auxiliary input for tuner, tape deck, CD player, etc.  
7. MIC Inputs - Balanced MIC level XLR inputs.  
8. Phantom Power - The CAM2 provides power for electret condenser microphones.The Phantom ON/OFF switch  
controls the applications of DC voltage to each MIC input.  
4
 
Input Connections  
Microphone Inputs  
Microphones are connected to the CAM2 using the MIC1 through MIC 4 connectors.The CAM2 uses male XLR  
type connectors for making connections to its inputs. Microphones typically accept female XLR connectors. Cables  
with male and female XLR connectors already attached are commonly available at retail stores or through Bogen.  
The figure below shows the connection of various microphones.  
Phantom Power  
Each MIC input has a PHANTOM switch associated with it.This  
switch must be set correctly for the type of microphone being  
used with that MIC input. Microphones come in two basic  
types: Dynamic and Electret Condenser.When using Dynamic  
microphones, set the PHANTOM switch for that microphone  
input to OFF. When using an Electret Condenser microphone,set the PHANTOM switch to ON.Elecret Condenser  
microphones require a DC voltage to power their internal circuitry.When the PHANTOM switch is set to ON, the  
microphone input will supply a DC voltage back to the Electret Condenser microphone through the microphone  
cable (this is called providing Phantom Power to the microphone).  
If the PHANTOM switch is set to ON when using a Dynamic microphone, you may hear a loud pop every time the  
microphones ON/OFF switch is changed. If you do hear this, then check that the PHANTOM switch for that micro-  
phone input is set properly.  
5
 
Input Connections  
Microphone Cable Wiring  
The CAM2 has female XLR connectors as its microphone inputs, these connectors have 3 pins and are designed to  
be connected to balanced, low-impedance microphones.These microphones require 3 connections and use a cable  
that has two insulated conductors and a shielding material that encases the conductors (the shield provides the third  
connection). The use of balanced microphones provides superior protection against the pickup of unwanted hum,  
noise, and interference. It allows long cables to be used to connect the microphones to the CAM2.  
The figure below shows how to wire the Male and Female XLR connectors onto a 2-conductor with shield cable  
to make custom microphone cables.  
AUX IN  
Certain music input sources, such as tape decks and CD players, send larger signal levels that  
microphone inputs are not suited to accept. Microphone inputs are very sensitive and if one  
of these devices were connected to a microphone input, then the output from the CAM2  
would be distorted and unusable.  
Since it is common to have recorded music mixed together with live sound from microphones, the CAM2 provides  
a single AUX input for the connection of a tape deck, CD player, tuner or similar equipment.The AUX IN connec-  
tion has the appropriate input sensitivity to accept signals from these types of equipment.The input uses an unbal-  
anced RCA connector which is typical of the output from playback equipment. RCA patch cords are readily avail-  
able for making connections to this input. However, this is a mono input so the output from a stereo source must  
be combined by a Y-adapter so that both halves of the stereo playback are heard.The AUX input is an unbalanced  
input.When using unbalanced inputs, it is a good idea to keep the length of the connecting cable to 10 feet or less.  
6
 
Output Connections  
BAL/OUT to Balanced Input of Other Equipment  
The CAM2 provides a balanced output signal from the male XLR connector labeled  
BAL/OUT. Many types of professional equipment, like power amplifiers, have balanced  
inputs that are compatible with this output.The figure below shows the connection to a  
balanced input that has screw terminals. Many balanced inputs use XLR connectors. For  
XLR inputs, a standard MIC cable can be used.The figure in the next section shows this  
type of cable.The balanced output provides the same type of protection from noise and  
interference that the balanced microphones have and requires 3 wires to make the con-  
nections. For the best results, use this output connector if running the CAM2 output  
over long distances. When using the BAL/OUT to feed amplification or recording equip-  
ment, set the OUTPUT LEVEL switch to the +4dB position.This position provides the  
larger output voltages (relative to the smaller microphone output signals) required by  
other equipment.  
BAL/OUT to Microphone Input of Other Equipment  
It is sometimes necessary to feed the CAM2 output to the microphone input of anoth-  
er piece of equipment. However, the signal level of the CAM2’s output must be at a volt-  
age level compatible with microphone inputs. Microphone inputs require much smaller  
signal voltages than the inputs of other equipment.To accommodate this requirement,the  
CAM2 OUTPUT LEVEL switch can be set to the -50dB position. In this position, the out-  
put level of the CAM2 will be reduced to one that is compatible with microphone inputs.  
The CAM2 BAL/OUT connector requires a female XLR connector and the microphone  
inputs of other equipment typically require a male XLR.Therefore, a female to male XLR  
cable must be used for this type of connection.The diagram below shows the wiring of  
this type of cable and also the correct OUTPUT LEVEL switch position for feeding micro-  
phone inputs.  
7
 
Output Connections  
LINE OUT  
Unbalanced inputs are also popular on many pieces of equipment that the CAM2 may feed.  
To make the connection as easy as possible, the CAM2 provides an unbalanced LINE OUT  
signal that is of the proper signal level to connect to most equipment.An RCA patch cord is  
used to make this connection and is commonly available at retail stores. Since this output is  
unbalanced, it is important to keep the length of the connecting cable relatively short. Less  
than 10 feet is recommended. The figure below shows the general way in which the LINE  
OUT of the CAM2 is connected to the unbalanced input of an amplifier.  
8
 
Bridging Mixers  
Bridging Connections  
In certain applications, more than four microphones or a single AUX input is needed. In these cases a CAM2 can be  
connected to another CAM2 to increase the number of inputs available.The BRIDGING connectors are provided  
for this purpose.To combine two to four CAM2 units together, connect an RCA patch cord between either of the  
BRIDGING connectors on one unit to either of the BRIDGING connectors of the other unit.The 2 RCA Bridging  
connectors on the CAM2 are wired together in parallel to allow units to be easily “daisy chained” together.The  
Bridging connectors provide access to the internal mix bus of each CAM2.When bridged together, the output of  
any of the CAM2 units can be used as the output to other equipment because the same output signal is present on  
each unit’s output. However, master volume control for all of the mixers will be the MASTER control on the CAM2  
whose output is being used. The MASTER control of all of the other units have no effect on system volume. See  
the section on operation for more information.  
Note: Bridging more than four CAM2 units together may reduce the maximum system output signal level below what is  
necessary to drive amplifiers and recording equipment.  
9
 
Operation  
Power  
This switch applies power to the unit.The SwitchActuator will light to indicate power "ON" when  
connected to an AC power source.  
MIC Gain Control  
The four MIC volume controls are used to adjust the level of individual mic input channels. Rotate  
these controls clockwise (to the higher numbers) to increase volume and counter-clockwise (to  
the lower numbers) to reduce volume. Use these controls and the AUX control to mix the input  
signals to the desired levels.  
AUX Gain Control  
Controls the AUX input volume and functions the same as the MIC volume controls.  
Clip Indicator  
Each input channel has a dedicated red clip-  
ping indicator to the right of the channel’s  
label. During normal operation, the CLIP  
indicators for each input should remain unlit or light infrequently.  
If the indicator is lighting frequently or constantly, it indicates that the input is being overdriven by too much input  
signal level.The input of the CAM2 can only accept signals up to a certain level. Once the input signal becomes larg-  
er than the handling capability of the input circuits, the circuitry will begin to distort the input signal. The distortion  
will produce poor sound quality on that channel.This condition is called overdriving the input.The distortion of the  
input signal cannot be corrected by turning down the input level control because the signal is being distorted before  
the level control can affect it. All the level control can do, in this case, is adjust the level of the now distorted sig-  
nal.To correct this situation, the level of the signal source must be reduced so that it is no longer overdriving the  
input.Typically, microphones will not overdrive their inputs. However, other equipment that is connected to a MIC  
input has a high likelihood of overdriving the input. Note that the -50dB setting of the CAM2 BAL/OUT’s Output  
Level switch was provided to avoid this very situation when a CAM2 BAL/OUT signal is connected to another MIC  
input.The AUX input can also be overdriven, but the signal levels necessary to do this are much higher than those  
of a MIC input. Normally using the outputs of CD players, tuners, and tape players will not cause this problem.  
However, connection to the speaker outputs of boom boxes, stereo amplifiers, and other equipment designed to  
drive speakers can overdrive the AUX input.  
Master Gain Control  
This control regulates the overall output level of the CAM2. After setting the MIC and AUX con-  
trols to provide the desired mix of input signal sources,adjust the MASTER control for the desired  
overall volume level throughout the audio system. The MASTER gain control affects both the  
BAL/OUT and LINE OUT signals.  
Output Level Meter  
The output level meter is provided as a tool for getting the optimum performance from the  
CAM2. Using the individual level controls and the master, adjust the levels as desired but below  
the level that caused the red +3 output level meter indicator to light (it can light infrequently on  
short peaks in the sound). If the output signal is very low, as in quiet passages in music, the out-  
put level meter may not light at all. It was designed to assist in the operation of the CAM2 as the  
output signal levels approach critical maximum output level. If the red indicator is flashing fre-  
quently or constantly, it means that the output signal from the CAM2 is becoming distorted and could be causing  
poor sound quality.Turn down the MASTER control, or the individual control of a particularly loud input, to bring  
the meter out of the red range. See the section on setting up system gains for further tips on levels.  
10  
 
Audio System Level  
Setting System Levels  
In audio systems that employ separate mixers and amplifiers, there are quite a few controls that affect the volume  
of a signal. Knowing how to set these different volume controls is instrumental to proper system operation. In gen-  
eral, the closer the control is to the signal source, the higher that control should be set.  
For example,an audio system contains a microphone,a CAM2,and a power amplifier.There are 3 controls that affect  
the volume of the microphone through the audio system speakers; the MIC input control, the CAM2 MASTER con-  
trol and the volume control on the amplifier. How should these be set for best operation? Since the MIC control  
is the closest (electrically), the microphone should be turned up the highest while still allowing enough “headroom”  
to increase the microphone volume if necessary.The MASTER control should then be adjusted to produce an out-  
put signal that lights up the red output meter indicator only on loud peaks and the volume control of the amplifier  
should be set so that the volume of the speakers are as loud as could possibly be needed. By setting the volume  
controls this way, the amount of undesirable hiss noise, which is produced in all audio equipment, is minimized.  
This is the correct theory in setting up system gains (volume levels). However, there are some other factors that  
ought to be considered. For instance, the individual input control should not be set so high that it requires the MAS-  
TER control to be set near zero to keep the output signal level out of the red.There has to be a reasonable amount  
of “control range” to the MASTER control to make it useful. In this case it is a good idea to reduce the level of the  
individual input control so that the MASTER control can be rotated over a wider range to provide some overall  
level control. During normal operation of a well set up audio system, the MASTER control is used to increase or  
decrease the overall system level as the noise and audience increases and decreases. However, large changes in the  
necessary volume level should be adjusted at the power amplifier. If the signal output level of the CAM2 is near its  
maximum (as indicated by the output level meter) and the desired speaker level cannot be achieved, even with the  
power amplifier volume at full, it indicates that the power amplifier or the size/quantity of the speaker is not ade-  
quate to cover the desired area.This type of problem cannot be corrected by system volume control settings.Trying  
to get more volume out of a system under these circumstance can only lead to distorted sound since the audio  
equipment will be pushed beyond their designed maximum operating conditions. Correct the problem by getting  
more suitable equipment for the job.  
It is typically desirable to get as much signal level from the output of the CAM2 without making it so large that the  
output circuit cannot maintain the signal level and begins to distort the signal.  
11  
 
Specifications  
Rated Output Levels  
Bal Out  
Line Out  
+4dBu or -50dBu (switch selected)  
0dBu  
Frequency Response  
+/- 1dB 20Hz to 20kHz  
Less than .5%  
Distortion at Rated Output  
Headroom  
10dB  
MIC Input Equivalent Input Noise  
MIC Input Sensitivity  
-123dBV (150 ohms source, 22Hz - 22kHz)  
300uV for rated output  
600 ohms  
MIC Input Impedance  
Aux Input Signal-to-Noise  
Aux Input Sensitivity  
-75dB (Ref to rated output level, 22Hz - 22kHz)  
70mV for rated output  
10k ohms  
Aux Input Impedance  
Bal/Out Output Impedance  
Bal/Out Nominal Load Impedance  
Line Out Output Impedance  
Line Out Nominal Load Impedance  
Crosstalk (adjacent channels)  
Phantom Power  
140 ohms (+4dBu positions)  
600 ohms  
50 ohms  
600 ohms  
Better than -90dB  
+12V DC  
Output Level Meter (Bar Graph)  
MIC Input Clipping LED  
Controls  
+3, 0, -3, -8, -12dB  
-29dBV (35mV)  
4 MIC controls  
1 AUX control  
1 MASTER control  
1 POWER switch  
4 Phantom Power switches  
BAL/OUT Output Level switch  
Temperature Range  
Power Consumption  
Dimensions  
-10 to +48oC; 14 to 120oF  
120V AC, 60Hz, .043A  
11-3/8" W x 2-7/8" H x 7-3/4" D  
4 lbs.  
Shipping Weight  
12  
 
LIMITED WARRANTY  
The Bogen CAM2 is warranted to be free from defects in material or workmanship provided that the product  
has not been subjected to abuse or accident or altered in any way for two (2) years from the date of sale to the  
original purchaser.Any part of the product covered by this warranty that, with normal installation and use,  
becomes defective will be repaired or replaced by Bogen, at our option, provided the product is shipped insured  
and prepaid to: Bogen Factory Service Department, 50 Spring Street, Ramsey, NJ 07446, USA.The product will be  
returned to you freight prepaid.This warranty does not extend to any of our products that have been subjected  
to misuse, improper storage, neglect, accident, improper installation or have been modified or repaired in any  
manner that Bogen believes may affect the reliability of the product, or where the serial number or date code has  
been removed or defaced.  
THE FOREGOING LIMITED WARRANTY IS BOGEN’S SOLE AND EXCLUSIVE WARRANTY  
AND THE PURCHASER’S SOLE AND EXCLUSIVE REMEDY. BOGEN MAKES NO OTHER WAR-  
RANTIES OF ANY KIND, EITHER EXPRESS OR IMPLIED,AND ALL IMPLIED WARRANTIES OF  
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE ARE HEREBY DISCLAIMED  
AND EXCLUDED. Bogen's liability arising out of the manufacture, sale or supplying of products or their use or  
disposition, whether based upon warranty, contract, tort or otherwise, shall be limited to the price of the product.  
In no event shall Bogen be liable for special, incidental or consequential damages (including, but not limited to, loss  
of profits, loss of data or loss of use damages) arising out of the manufacture, sale or supplying of products, even if  
Bogen has been advised of the possibility of such damages or losses.  
Products that are out of warranty will also be repaired by the Bogen Factory Service Department -- same address  
as above or call 201-934-8500. The parts and labor involved in these repairs are warranted for 90 days when  
repaired by the Bogen Factory Service Department. All shipping charges in addition to parts and labor charges will  
be at the owner's expense.  
13  
 
50 Spring Street, Ramsey, NJ 07446, U.S.A.  
Tel: 201-934-8500 Fax: 201-934-9832; www.bogen.com  
 

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