Page 1
CVA Series
Owner’s Manual
April 2010
www.stewartaudio.com
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Important Safety Instructions
Before using your Stewart Audio Inc. Power Amplifier, please read this
Owner’s Manual carefully to ensure optimum trouble-free performance.
WARNING: TO REDUCE THE RISK OF ELECTRICAL SHOCK, DO NOT EX-
POSE THIS AMPLIFIER TO RAIN OR MOISTURE. DANGEROUS HIGH
VOLTAGES ARE PRESENT INSIDE THE ENCLOSURE. DO NOT OPEN THE
CABINET. REFER SERVICING TO QUALIFIED PERSONNEL ONLY.
The lighting bolt within arrowhead symbol, within an
equilateral triangle, is intended to alert the user to the
presence of un-insulated “dangerous voltage” within
the product’s enclosure that may be of sufficient magnitude to constitute a risk of electrical shock to person.
The exclamation point within an equilateral triangle, is
intended to alert the user to the presence of important
operating and maintenance (servicing) instruction in the
literature accompanying the appliance.
Important Safety Instruction – Please Read Prior to Product
Installation.
1. Installation should be performed by a trained and licensed professional to
insure safe and lasting operation.
2. All of the safety and operating instructions should be read before the am-
plifier is installed or operated. Retain these instructions for future reference. All instructions should be followed; all warnings on the amplifier
and in the operating instructions should be adhered to.
3. The amplifier should be situated so that its location and position does not
interfere with its proper ventilation. For example, the amplifier must not
be placed on a rug, bed, sofa or similar surface that impedes airflow
across the chassis. Airflow around the unit should be unobstructed.
4. This amplifier should not be used near water, for example, near a bathtub,
in a wet basement, near a swimming pool, etc. This amplifier is intended
to be operated in a controlled indoor environment.
5. Do not place the amplifier near heat sources such as radiators, heat registers, stoves, or other appliances that produce heat.
6. The amplifier’s power supply should only be connected to 120 VAC, 60
Hz power source. Do not defeat the ground or polarization of the power
plug.
7. Route power cord and other cables so that they are not likely to be
walked on, tripped over or stressed. Pay particular attention to condition
of cords and cables at plugs and at the point where they exit the amplifier. To prevent risk of fire or injury, damaged cords and cables should be
replaced immediately.
8. Clean the amplifier with a clean, damp cloth. Do not use solvents or abrasive cleaners. Never pour any liquid on the amplifier.
9. When left unused for a long period of time, the power cord should be
unplugged from the outlet.
10. Damaged Amplifiers requiring service should be repaired by a qualified
service technician when:
a. The power cord or AC plug has been damaged.
b. Objects have fallen, or liquid has spilled into the unit.
c. The amplifier has been exposed to rain or other moisture.
d. The amplifier does not appear to operate normally or exhibits
a marked change in performance.
e. The amplifier has been dropped or the enclosure
damaged.
11. The user should not attempt to service the amplifier beyond that described in the operating instructions. All other servicing should be referred
to qualified service personnel.
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Table of Contents
Important Safety Instructions ······························································ 2
Table of Contents ················································································ 4
1 Welcome ························································································· 5
1.1 Features ··············································································· 5
1.2 Using this Manual ································································ 5
2 Setup ······························································································· 6
2.1 Setup Precautions ······························································· 6
2.2 Amplifier Installation ···························································· 6
2.2.1 Pole-Mount Installation ··········································· 6
2.2.2 Universal-Mount Installation ··································· 7
2.2.3 Product Dimensions ··············································· 8
2.3 Proper Cooling Considerations ············································ 8
2.4 Input Connections ······························································· 9
2.4.1 Balanced Input Connections ··································· 9
2.4.2 Unbalanced Input Connections ····························· 10
2.5 Output Connections ·························································· 11
2.5.1 Constant Voltage ················································· 11
2.5.2 Wiring Example ···················································· 12
3 Operation ······················································································ 13
3.1 Operation Precautions ······················································· 13
3.2 Controls, Indicators, and Connectors ································ 14
3.2.1 Indicators ······························································ 15
3.2.2 Controls ································································ 15
3.2.3 Remote Volume Control ······································· 15
4 Troubleshooting ··········································································· 17
5 Technical Specifications ······························································ 18
6 Warranty Information ·································································· 19
6.1 Warranty Summary ···························································· 19
6.1.1 Eligibility for Factory Repair ·································· 19
6.2 Return Procedure ······························································ 19
6.2.1 Return Authorization ············································· 20
6.2.2 Packaging Instructions ·········································· 20
6.2.3 Shipping Instructions ············································ 20
6.2.4 Estimate Approval ················································· 21
6.2.5 Payment of Non-Warranty Repair ························· 21
7 Accessories ··················································································· 22
This amplifier proudly designed and manufactured in the USA.
1 Welcome
Congratulations on the purchase of your new Stewart Audio CVA Series power amplifier. This amplifier has been designed and built to provide you with years of high-quality audio performance and trouble-free
operation. If after reading this manual you should have any questions
concerning amplifier installation and operation, please contact your Authorized Stewart Dealer, or you may contact us directly using the contact information provided on the back of this manual.
1.1 Features
Your Stewart Audio CVA Series amplifier is the result of years of experience in the design and manufacture of quality amplifiers. As such it
provides a combination of performance and operational benefits that
simply cannot be found in conventional amplifiers.
Sub Compact 1/4 rack package
Mono constant voltage amplifier (25V or 70.7V)
Music and fire alarm muting
Clean full–range dynamic power
Remote volume control
Multiple mounting options
External inline power supply
Made in the USA
1.2 Using this Manual
In order to obtain maximum performance from your CVA Series Amplifier, please take time to read this brief owner’s manual and carefully
follow the guidelines for connection and operation.
This manual provides you with the information necessary to safely install and operate your new CVA Series amplifier in the most common
scenarios. If you find yourself requiring additional assistance, please
feel free to contact your Authorized Dealer, or you may contact us directly using the contact information provided on the back of this manual.
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2 Setup
2.1 Setup Precautions
CAUTION: Before installing your amplifier, make sure that
you have read the Important Safety Precautions at the beginning of this manual.
2.2 Amplifier Installation
The CVA Series incorporates a number of different mounting options in
order to fit your installation needs.
2.2.1 Pole-Mount Installation
The CVA Series amplifier casing has mount holes on both the top as
well as the side of the unit which can be used with the AV-Pole bracket
available from Stewart Audio. Two screws are included in the kit which
will affix the bracket to the top or side of the unit.
Part Number: AV-Pole
2.2.1 Universal-Mount Installation
The CVA Series also has a universal bracket available which allows the
unit to be mounted against a wall or under a table. Two screws are
included in the kit which will affix the bracket to the top or the side of
the unit. Once this is done, two holes are available for mounting the
unit where desired.
CAUTION: Use only the screws provided in mounting
brackets to the amplifier. Do not overtighten.
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2.2.3 Product Dimensions
2.4 Input Connections
Your CVA Series amplifier is provided with a 3-pin Euro Block connector
for its input connection. This connector will accept both balanced or
unbalanced connections, however some modifications must be made
for an unbalanced connection. See the next two sections for instructions on connecting your amplifier to its input source.
2.4.1 Balanced Input Connections
When using a balanced input source and connector, you must ensure
that the hot, cold, and ground pins of the connector are matched up to
the +, -, and ground pins of the CVA Series’ Euro Block connector respectively. Diagrams have been provided for standard XLR and TRS
connectors. Please refer to the manual of your input source in case it
does not follow the standard pin-out.
2.3 Proper Cooling Considerations
Because CVA Series amplifiers regulates their temperature using convection cooling and no fans, the amplifiers must be given adequate
space to allow for proper airflow. Do not stack the amplifiers on top of
each other or mount it in a way that other equipment will block airflow
along the surfaces of the case.
CAUTION: Inadequate airflow to the amplifier can cause the
amplifier to overheat and potentially become damaged in
the process. Be sure to provide plenty of air space to allow
for convection cooling.
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NOTE: The CVA Series of amplifiers do not
puts wired for a stereo source. TRS inputs should only be
used for balanced mono inputs.
accept TRS in-
Page 6
2.4.2 Unbalanced Input Connections
When using an unbalanced input source and connector, a jumper must
be added between the negative (-) terminals and the ground terminals.
Once this has been done, the unbalanced source can be connected to
the positive (+) and ground terminals. Please refer to the manual of
your input source in case it does not follow the standard pin-out. For
your convenience, pre-wired connectors are available for purchase, see
the next page for details.
NOTE: A jumper is required for connecting an unbalanced
input.
NOTE: The CVA Series of amplifiers do not accept stereo
inputs. Either one side must be selected from the stereo
source or an overload-protected
sum them to mono. It is highly recommended that you
purchase the pre-wired connectors mentioned on the next
page. Damage to source equipment can result from the
use of a standard Y-cable.
Y-cable must be used to
Pre-wired unbalanced connectors are available for purchase from Stewart Audio. These will allow for a quicker installation with less room for
error when connecting the CVA Series amplifier to an unbalanced
source. The summing adapters will properly sum a stereo source for
use with the mono input on the rear of the amplifier without causing
sound cancellation. Part numbers are found below the diagrams.
ADPT-RCA
Mono
Female RCA
ADPT-SUMRCA
Stereo
Female RCA
Female 3.5mm
ADPT-SUM35
Stereo
2.5 Output Connections
Because of the differences in the way that constant-voltage amplifiers
work as opposed to a typical 8-ohm setup, the wiring procedure and
the gauge of wire used is very different.
Constant voltage systems and speakers use a smaller current flow than
the typical 8ohm systems and thus can use a higher gauge (thinner
diameter) wire. Please refer to the following g chart to choose the appropriate wire gauge for your installation.
Speaker leads connect by means of removable Euro Block connectors
supplied with the unit. Strip speaker leads 1/4” and insert leads into
connector observing proper polarity. With a small, flat-blade screwdriver, tighten the screw until the leads are held securely in place. Inspect for possible shorts or broken wires.
Distance Wire Gauge
Up to 500ft 22 AWG
500-1000 ft. 20 AWG
Over 1000ft 18 AWG
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2.5.1 Constant Voltage
The Euro Block connector on the rear of the amplifier is capable of supplying output at either 25V or 70V depending on the step-down transformers which will be used in the speaker installation. For information
on specific step-down transformer installation information, please consult the transformer’s manufacturer’s literature.
2.5.2 Wiring Example
The diagram below is a typical wiring setup for two speakers with outboard step-down transformers wired in parallel to the 70V output option of a CVA Series amplifier.
3 Operation
3.1 Operating Precautions
1. Before use, your amplifier must be configured for proper operation, including input and output wiring hookup. Improper wiring
can result in damage to equipment or potentially harm to the
operator. Consult section 2 for setup instructions.
2. Tampering with the circuitry, or making unauthorized changes
is not only dangerous but may also violate local regulations.
3. Use care when making connections between the amplifier and
the input or output equipment. Using equipment that is not
capable of handling the output wattage may lead to permanent
damage.
NOTE: Stewart Audio will not be held responsible for
damage to your CVA Series amplifier or connected equipment if the instructions in this manual are not followed.
NOTE: For additional operating precautions, please refer
to “Important Safety Instructions” located on Page 2.
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3.2 Controls, Indicators, and Connectors
1
2
3
6
7
8
4
5
1
2
3
6
7
8
4
5
CVA 25-1
3.2.1 Indicators
CVA Series amplifiers have three rear panel LEDs to indicate the status
of the amplifier. The blue LED, labeled “ON”, will be lit when the unit
is not in sleep mode. The green LED, labeled “SIG”, will light when an
audio signal is present on the audio input. When the unit is operating
with both green and blue LEDs lit and the audio input signal goes away
or is removed, the green “SIG” LED will go out and the unit will continue to operate with the blue LED on for approximately 5 minutes before going into sleep mode. When signal is present and output is going
to the speakers the red LED, labeled “Clip”, will light when the input
signal is too hot. The “LEVEL” control must be adjusted until the CLIP
LED goes out for undistorted sound amplification.
LEVEL
+10V
RVC
GND
RVC
MUTE
ON SIG CLIP
Clip Indicator LED
Power Connector
Output Connector
- +
INPUT
Volume Level Knob
1
Input Connector
Remote Volume Control
Power Indicator LED
Signal Present Indicator LED
14 15
PLENUM RATED
+
PWR
SPEAKER
25V 70V
+ +
3.2.2 Controls
All CVA Series controls are located on the rear of the unit. There is no
power switch so the amplifier will power up into a sleep state when
power is first applied. The CVA Series Signal Sense Technology (SST™)
will power up the amplifier from sleep when a signal is detected. After
5 minutes without an input signal the amplifier will go into sleep mode.
The rear panel contains a single volume knob. The amplifier is set to
run off of a line-level source and the level should be adjusted for optimum performance. To adjust this knob, you will need a small flat-head
screwdriver. While a typical program source level is present, spin the
rotary knob as far clockwise as you can without hearing distortion or
without the “Clip” indicator illuminating. If the signal is distorting and
the knob is all the way counter-clockwise, adjust the gain down at the
source level.
3.2.3 Remote Volume Control
CVA Series amplifiers can have their volume remotely controlled (or
muted) via the Euro Block input on the rear of the amplifier. The remote
volume control allows the units volume to be controlled through the
use of an external potentiometer which can be located wherever convenient for the user. Remote muting is also useful for fire-alarm situations in which all unnecessary sound must be silenced.
NOTE: If the remote volume control connector is utilized,
it will override the volume knob on the rear of the unit.
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3.2.3 Remote Volume Control (cont.)
In order to remotely control the volume of the unit, a 10k-ohm potentiometer should be placed between the +10V pin and the GND (Ground)
pin on the rear of the unit with its wiper on the RVC pin. The volume
will be determined by the selected resistance on the potentiometer,
the greater the resistance the louder the volume.
The amplifier can be remotely muted by making a connection between
the GND pin and the MUTE pin. No power should be applied to these
pins, simply a contact connection.
4 Troubleshooting
Problem: Power indicator does not turn on.
Procedure: Check that the unit’s power supply is plugged into a func-
tioning outlet and the power supply is correctly connected to the unit.
Ensure that there is an audio signal present on the audio input indicated
by the green LED being lit. If the unit is powered up but in sleep mode
(due to no signal), the blue power LED will not be lit.
Problem: No output heard on speakers; Blue power indicator is lit.
Procedure: Check that level controls are not turned down. Check that
input and output connections are secure. Ensure signal present LED is
lit to denote a signal. If there is no signal detected check signal source
and that level controls are set high enough.
Problem: Amplifier overheats and/or shuts off.
Procedure: Review section 2.3 on proper cooling procedures. Check
the clip LED on the rear of the amplifier to see if the signal is overdriving (the signal light flashes red frequently). Overdriving the amplifier for
extended periods of time can cause a thermal shutdown.
Problem: Output sound is distorted or cracking.
Procedure: Check all cables for damage or loose connections and re-
duce the gain on the input signal at the mixer or preamp level. Replace
the cables and loudspeakers temporarily to see if this resolves the
problem. If problem still exists, contact your Authorized Dealer for service.
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5 Technical Specifications 6 Warranty Information
Maximum Output 30Hz - 20kHz
CVA-25 25W @ 25V/70V
CVA-50 50W @ 25V/70V
Frequency Response (+0, -3 dB)
Power Bandwidth +/- 3dB
THD+N
Signal-to-Noise Ratio
Remote Volume Control
Input Sensitivity
Standard Voltage Gain
Input Impedance (Balance/Unbalanced)
Sleep, Idle Current Draw, 1/8 Draw
Class
Input Connectors
Output Connectors
Power Supply
Cooling
Controls
LED Indicators
Construction
Plenum Rating
Dimensions
Height 1.25in (3.2cm)
Width 4.35in (11.1cm)
Depth 3.2in (8.1cm)
Weight CVA-25/CVA-50 <0.7bs (0.32)/
Stewart Audio reserves the rate to change features and specifications without notice.
100Hz—20kHz
80Hz-30kHz
<0.1%
>80dB
0-10V DC, 4-pin Block
.5V (-3 dBV)
151X (43dB) @ 70.7V
20k Ohms/10k Ohms
0.005/0.01/0.15 Amps
D
Euro Block 3-pin, 3.5mm
Euro Block 2-pin, 5mm
External In-Line 48DVC
Convection-Cooling
Level
Power, Signal, Clip
Aluminum Chassis
UL 2043 Approved
1.2 lbs (0.54kg)
6.1 Warranty Summary
All Stewart Audio amplifiers and accessories, unless excluded in this
summary, are covered by a 3-year limited warranty on parts and labor
from the data of purchase. In order to be eligible for warranty repairs,
the amplifiers and accessories must have been purchased through an
authorized Stewart Audio dealer and submitted by the original purchaser. This warranty is only valid in the country in which the amplifier
was purchased.
6.1.1 Eligibility Requirements.
Stewart Audio warrants against all malfunctions which come as a result
of component or manufacturer defect. The amplifier is also covered
from all failures which arise during the warranty period (3 years from
date of purchase) that are not a result of misuse. The following actions
will void your warranty:
The power cord or AC plug has been damaged through misuse.
The amplifier has been exposed to moisture or extreme tempera-
tures.
The amplifier has been dropped, items have been dropped on the
amplifier, or the enclosure has been damaged.
The amplifier has been opened by the operator.
The amplifier was improperly packaged when sending to the fac-
tory for repair, resulting in damage.
Any of the precautions or instructions found in this manual were
not followed.
Damages resulting to the amplifier which are not covered under this
warranty can be factory-repaired at cost to the customer. Use the contact information below to initiate the repair process.
6.2 Return Procedure
This section includes the return procedures which must be followed in
order to prevent processing delay or cost to the customer. Please read
the entire section before contacting Stewart Audio for returns.
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6.2.1 Return Authorization Number
All returns to the factory for service must be accompanied by a Return
Authorization (RA) number. One can be obtained by contacting Stewart
Audio at (209) 588-8111 or via e-mail at support@stewartaudio.com.
NOTE: Any defective products received without an RA number will
be returned to sender at their expense.
If Stewart Audio is unable to contact the sender in 14 days, the merchandise will be considered scrap and may be disposed of.
6.2.2 Shipment Instructions
If Stewart Audio requests that you ship the defective product back to
their service center, please refer to the guide below. To ensure prompt
warranty service, be sure to follow all instructions.
1. Return Authorization (RA) is required for product being sent to the
factory for service.
2. See packing instructions in section 6.2.3.
3. Ship the defective product using a method which provides for order tracking or order confirmation. The service center is located at
the following address:
Stewart Audio
14397 Cuesta Court Suite D1
Sonora, CA 95370
4. Use a bold black marker and write the RA number on three sides
of the box.
5. Record the RMA number for future reference. The RA number can
be used to check the repair status.
6.2.3 Packaging Instructions
Should Stewart Audio request that you ship your product to their service center, these instructions must be followed in order to ensure safe
delivery. If they are not followed, Stewart Audio assumes no responsibility for damaged goods and/or accessories that are sent with your
unit.
6.2.3 Packaging Instructions (cont.)
1. Please write the RA number on three sides of the box. Include the
Stewart Audio RA number inside the box and a brief description of
the problem.
2. Do not ship any accessories (manuals, cords, hardware, etc.) with
your unit. These items are not needed to service your product.
Stewart Audio will not be held responsible for these items if they
are returned with the amplifiers.
3. When shipping your amplifier, it is important that it has adequate
protection. We recommend you use the original packing material
when returning the product for repair. If you do not have the original box, see number 4.
4. If you provide your own shipping pack, the minimum recommended requirements for materials are as follows:
a. 275 P.S.I. burst test, Double-Wall carton that allows for 2-
inch solid Styrofoam on all six sides of unit or 3 inches of
plastic bubble wrap on all six sides of unit.
b. Securely seal the package with an adequate carton sealing
tape.
c. Do not use light boxes or “peanuts”.
NOTE: Damage caused by poor packaging will not be covered under warranty.
6.2.4 Estimate Approval
An estimate for all non-warranty repairs will be provided to the customer once the unit has been shipped to the factory. The customer is
responsible to approve this estimate within 7 days. If the repairs are
not approved within 14 days, Stewart Audio reserves the right to consider the unit scrap and may discard it.
6.2.5 Payment of Non-Warranty Repairs
Payment for non-warranty repairs must be submitted to Stewart Audio
before the product will be returned to the customer.
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7 Accessories
The following accessories are available from Stewart Audio for your
amplifier.
All part numbers shown are Stewart Audio Part Numbers.
Mounting Brackets
AV-POLE Pole-mount bracket for AV Series amplifiers
AV-BRACKET Universal mounting bracket for AV Series amplifiers
Connection Adapters
ADPT-RCA Mono Female RCA to male Euroblock.
ADPT-SUMRCA Stereo Female RCA to male Euroblock.
ADPT-SUM35 Stereo Female 3.5mm to male Euroblock
Wall Plates
WP-RVC-B Wallplate with 10k potentiometer and knob for re-
mote volume control (Black)
WP-RVC-A Wallplate with 10k potentiometer and knob for re-
mote volume control (Aluminum)
To purchase these accessories or to see the full
Stewart Audio product lineup, visit us at:
www.stewartaudio.com
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