Crest audio FXA User Manual

PROFESSIONAL POWER AMPLIFIERS

FXA

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OWNER’ S MANUAL

Important Precautions

This symbol is used to alert the oper­ator to follow important operating
procedures and precautions detailed
in documentation.

This symbol is used to warn opera­tors that uninsulated “dangerous volt­ages” are present within the equip­ment enclosure that may pose a risk
of electric shock.

1. Save the carton and packing material
even if the equipment has arrived in
good condition. Should you ever need

to ship the unit, use only the original
factory packing.

2. Read all documentation before oper­ating your equipment. Retain all doc-

umentation for future reference.

3. Follow all instructions printed on unit
chassis for proper operation.

4. Do not spill water or other liquids

into or on the unit, or operate the unit
while standing in liquid.

5. Make sure power outlets conform to

the power requirements listed on the
back of the unit.

6. Do not use the unit if the electrical

power cord is frayed or broken. The
power supply cords should be routed so
that they are not likely to be walked on
or pinched by items placed upon or
against them, paying particular atten­tion to cords and plugs, convenience
receptacles, and the point where they
exit from the appliance.

7. Always operate the unit with the AC

ground wire connected to the electri­cal system ground. Precautions should
be taken so that the means of ground­ing of a piece of equipment is not
defeated.

8. Mains voltage must be correct and

the same as that printed on the rear
of the unit. Damage caused by connec-

tion to improper AC voltage is not cov­ered by any warranty.

10. Power down & disconnect units from

mains voltage before making connec­tions.

11. Never hold a power switch in the
“ON” position if it won’t stay there
itself!

12. Do not use the unit near stoves, heat
registers, radiators, or other heat
producing devices.

13. Do not block fan intake or exhaust
ports. Do not operate equipment on a

surface or in an environment which
may impede the normal flow of air
around the unit, such as a bed, rug,
weathersheet, carpet, or completely
enclosed rack. If the unit is used in an
extremely dusty or smoky environ­ment, the unit should be periodically
“blown free” of foreign matter.

14. Do not remove the cover. Removing
the cover will expose you to potentially
dangerous voltages. There are no user
serviceable parts inside.

15. Connecting amplifier outputs to

oscilloscopes or other test equipment

while the amplifier is in bridged mode
may damage both the amplifier and test
equipment!

16. Do not drive the inputs with a signal

level greater than that required to
drive equipment to full output.

17. Do not connect the inputs / outputs
of amplifiers or consoles to any other
voltage source, such as a battery,

mains source, or power supply, regard­less of whether the amplifier or console
is turned on or off.

18. Do not run the output of any amplifi-

er channel back into another chan­nel’s input. Do not parallel- or
series-connect an amplifier output
with any other amplifier output.

Crest Audio is not responsible for dam­age to loudspeakers for any reason.

20. Non-use periods. The power cord of

equipment should be unplugged from
the outlet when left unused for a long
period of time.

21. Service Information Equipment

should be serviced by qualified service
personnel when:

A. The power supply cord or the plug

has been damaged;

B. Objects have fallen, or liquid has

been spilled into the equipment;

C. The equipment has been exposed to

rain;

D. The equipment does not appear to

operate normally, or exhibits a
marked change in performance;

E. The equipment has been dropped,

or the enclosure damaged.

22. To obtain service, contact your nearest

Crest Audio Service Center,
Distributor, Dealer, or Crest Audio at

201.909.8700 (USA).

9. Have gain controls on amplifiers
turned down during power-up to pre­vent speaker damage if there are high
signal levels at the inputs.

19. Do not ground any red (“hot”) ter-

minal. Never connect a “hot” (red)
output to ground or to another “hot”
(red) output!

Power Amplifier Owner’s Manual

Table of Contents

FXA

Introduction

Unpacking

Installation and Mounting

Front Panel

Rear Panel

Internal Configuration and Control

Operation

Connecting Power / Circuit Size Requirements

Cooling Requirements

Connecting Inputs

Connecting Outputs

Mode Selection

Stereo /Parallel/Bridged Mono Connections

TourClass®Protection Features

User Precautions

Speaker Protection

Recommended Speaker Cabling

Maintenance

User Responsibility

Service and Repair

5
5
5
6
7
8
9
9
9
10
10
10
11
12
13
13
13
14
14
14

Appendix A Specifications
Appendix B FXA Block Diagram
Appendix C Wire Gauge Charts
Appendix D Rear Panel Symbols - Legend

Appendix E FXA4801 Power Amplifier - Special Functions
Appendix F Warranty Information

Crest Audio FXA Series Power Amplifiers Page 3
Models FXA601, FXA901, FXA1201, FXA2401, FXA3601, FXA4801

FXA

FXA3601, FXA4801 Front View

Front

height

5.25"

133mm

Front

height

3.5"

89mm

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Front width 19" / 483mm

FXA601-FXA2401 Front View

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Front width 19" / 483mm

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Rear/Side Views and Dimension Information

FXA2401

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17.9"/437mm (19"/483mm to rack ears)

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CA2

FXA1201

CA4

3.5"
89mm

FXA901

CA6
CA9

FXA601
FXA301

FXA3601

CA12

5.25"
133mm

CA18

FXA4801*

1.375"

35mm

18"/457mm

*See Appendix E for detailed FXA4801 rear panel drawings.

Page 4 Crest Audio FXA Series Power Amplifiers

Models FXA601, FXA901, FXA1201, FXA2401, FXA3601, FXA4801

FXA

Introduction

Congratulations on your purchase of a new FXA Series professional power amplifier, and thank you for
your confidence in Crest Audio products. You are among the growing number of audio professionals who
have made Crest Audio one of the world’s leading suppliers of professional and commercial/industrial audio
systems.

For your safety, please read the Important Precautions section before installing and operating the amplifier.
The Crest Audio FXA Series is based on the same advanced circuit topologies that have made Crest ampli-

fiers the choice of touring professionals worldwide. FXA Series amplifiers are designed for high operating
efficiency and accurate sonic performance across the full audio bandwidth, even under stressful conditions.
In order to maintain strict quality assurance standards, all FXA Series amplifiers are built in Crest’s state-of­the-art USA manufacturing facility. Internal components are the finest available, and key sub-assemblies are
pre-tested before final assembly. Finally, each amplifier is “burned in” and thoroughly tested (using preci­sion audio test equipment) before shipping. In addition, all FXA Series amplifiers incorporate Crest’s exclu­sive TourClass®protection features to safeguard both internal circuitry and connected loudspeakers.

This proven combination of advanced design, quality construction, and comprehensive circuit protection is
your guarantee of fail-safe reliability. You can depend on consistent, stable performance even when your
FXA Series amplifier is subjected to punishing extremes in the most demanding fixed or mobile sound rein­forcement applications.

Unpacking

Please inspect the amplifier carefully immediately after unpacking. If you find any damage, notify your sup­plier/dealer immediately. Only the shipper may file a damage claim with the carrier for damage incurred
during shipping. Be sure to save the carton and all packing materials for the carrier’s inspection.

If your packing materials are in good condition, please save them. If you ever need to ship the unit back to
Crest Audio or an authorized service center, you should use only the original factory packing.

Installation and Mounting

Four FXA Series amplifiers are 2-rack-space units: models FXA601, FXA901, FXA1201, and FXA2401.
Models FXA3601 and FXA4801 are 3-rack-spaces high. All mount in standard 19-inch racks. Four front­panel mounting holes are provided on each amplifier. Rear mounting ears give additional support, and use
of rear supports is highly recommended in all mobile and touring sound systems.

Crest Audio FXA Series Power Amplifiers Page 5
Models FXA601, FXA901, FXA1201, FXA2401, FXA3601, FXA4801

FXA

Front Panel

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1. Rack Mounting Ears.

Two front panel mounting holes are provided on each mounting ear.

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Never try to hold the
circuit breaker/power
switch in the “ON”

2. Fan Outlet Grills.

FXA Series amplifiers are cooled by two, rear-mounted fans.

position if it won’t stay
there itself!

Cool air flows over the heat sinks and exhausts through the front grills.
Make sure these outlets remain clear to allow unrestricted air flow.

3. AC Power Switch/Circuit Breaker.

FXA Series amplifiers have a front-panel combination AC switch and circuit breaker. (No fuses are used.) If
the switch shuts off during normal use, push it back to the “ON” position once. If it will not stay on, the
amplifier needs servicing.

4. Clip LED.

Illuminates at the clipping threshold. Continuous illumination also indicates that ACL (Active Clip
Limiting) protection circuitry is engaged.

5. Signal LED.

Illuminates to indicate that a signal (above a minimum threshold) is present at the amplifier input, and that
the signal is being amplified.

6. Protect LED.

Indicates that the channel is in Protect mode (speakers disconnected by output relay).

7. Active LED.

Indicates that AC power is connected and the amplifier is turned on.

8. Input Attenuators.

Two input attenuators adjust level for their respective amplifier channels. In Bridged Mono Mode, both
attenuators are used to control signal level and must be adjusted to the same setting.

Page 6 Crest Audio FXA Series Power Amplifiers

Models FXA601, FXA901, FXA1201, FXA2401, FXA3601, FXA4801

Rear Panel See Appendix E for information specific to model FXA4801.

FXA

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Designed & manufactured in the USA by:

Crest Audio Inc.

100 Eisenhower Dr.

Paramus, New Jersey 07652 USA

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9. Output Connectors

CAUTION

RISK OF ELECTRIC SHOCK

DO NOT OPEN

AVIS : RISQUE DE CHOC ÉLECTRIQUE—NE PAS OUVRIR

WARNING TO REDUCE THE RISK OF FIRE OR ELECTRIC SHOCK DO NOT

EXPOSE THIS EQUIPMENT TO RAIN OR MOISTURE.

ATTENTION! POUR ÉVITER LE RISQUE D'INCENDIE OU DE CHOC

ÉLECTRIQUE, NE PLACEZ PAS CET APPAREIL SOUS LA PLUIE OU Á

L'HUMIDITÉ

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FXA Series amplifiers are supplied with 5-way Binding Posts. Connection to the binding posts can be made
with bare wire, banana plugs, or spade lug terminations. Make connections to both the Channel A and
Channel B terminals for Stereo or Parallel Mode, or a single connection across the red (“hot”) terminals
only of Channels A and B for Bridged Mono Mode. See Appendix D and the section on Mode Selection for
more information. NOTE: on the of the FXA4801, two pairs of 5-way binding posts are provided for each

channel, so that paralleling of speakers is possible.

10. Mode Selection Switch.

Never connect a “hot” (red) output to ground
or to another “hot” (red) output!

This recessed, three-position switch configures the
amplifier for Stereo, Parallel or Bridged Mono Mode operation. Amplifiers are factory-configured for
Stereo Mode. See Appendix D and the section on Mode Selection for more information.

11. Signal Ground Lift Switch.

The recessed signal ground lift switch (factory-set to the ‘ground’ [bottom] position) electrically connects
signal ground to the chassis/AC ground. The top position lifts the amplifier’s signal ground. In a properly
designed system (for safety purposes and to minimize noise), amplifiers should be connected to ground
through the AC line cord. Also, whenever possible, the signal source equipment should share the same AC
ground as the amplifier. In some cases this may not be possible, and a ground loop results. If this happens,
the first step is to move the ground lift switch to the top (‘lift’) position. In this position, the signal ground is
lifted and completely isolated from the chassis/AC ground. Do not change the switch to the ‘lift’position if
the amplifier and the signal source equipment are on the same AC ground. Should the ground loop problem
persist after the ground lift switch has been set to the ‘lift’ position, then the shield on balanced input lines
should be grounded at one end only (usually the signal source).

12-13. Balanced 1/4" (TRS) & XLR Input Connectors.

These connectors accept input signals on balanced TRS and XLR input plugs. See the figure on page 8 for
information on polarity. Connectors for each channel are in parallel; the unused connectors may be used for
“loop through” connection to other amplifiers.

NOTE: Unbalanced “Tip/Sleeve” plugs may be used with the balanced TRS “Tip/Ring/Sleeve” connectors.
The “ring” terminal or negative input will be connected to ground internally. When using three-pole
(‘stereo’) TRS connectors, make sure that the ring connection is made either to the cold (–) output of the
source equipment, or to ground. Incorrect connections may cause a 6dB loss in level.

Crest Audio FXA Series Power Amplifiers Page 7
Models FXA601, FXA901, FXA1201, FXA2401, FXA3601, FXA4801

FXA

14. Fan Inlet Ports & Filters.

Cooling air enters the amplifier through the fan inlet ports located on the rear of the amplifier chassis. Be
sure not to block these ports when installing the amplifier or other associated equipment. Air must flow
unimpeded through these ports. Fan filters (removable without tools) are provided to minimize entry of dust
and dirt.

Tip - Positive (+)

Internal Configuration and Control

Input XLR Polarity

FXA Series amplifiers are supplied standard with the XLR configured as “Pin 2
hot” (+). On models FXA601, FXA901, FXA1201, FXA2401 and FXA3601,
an internal jumper makes it possible to alter the amplifier to “Pin 3 hot” (+).
The FXA4801, features an external XLR polarity switch. (See Appendix E).

Ring - Negative (-)
Sleeve - Ground ( )

+

NOTE: This jumper is NOT user configurable. Please consult your supplier or
local Crest Audio service center if you wish to have the input XLR polarity
changed

Input Sensitivity

1 - Ground ( )

3 - Negative (-)
2 - Positive (+)

The FXA Series amplifiers have a standard input sensitivity of .775 Volts for rated power at 8 Ohms.
Models FXA601, FXA901, FXA1201, FXA2401 and FXA3601 are fitted with an internal jumper which
allows optional gains of X20 or X40. Model FXA4801 features an external voltage gain/input sensitivity
switch (See Appendix E). Standard and optional voltage gains/input sensitivities are detailed below.

FXA601 FXA901 FXA1201 FXA2401 FXA3601 FXA4801

Gain Sens Gain Sens Gain Sens Gain Sens Gain Sens Gain Sens

Std. X45 .775V X61 .775V X68 .775V X86.5 .775V X97.5 .775V X115 .775V
Opt. 1 X40 .866V X40 1.12V X40 1.32V X40 1.66V X40 1.87V X40 2.24V
Opt. 2 X20 1.73V X20 2.24V X20 2.65V X20 3.32V X20 3.74V X20 4.47V

NOTE: This jumper is NOT user configurable. Please consult your supplier or local Crest Audio service
center if you wish to have the voltage gain / input sensitivity changed.

Page 8 Crest Audio FXA Series Power Amplifiers

Models FXA601, FXA901, FXA1201, FXA2401, FXA3601, FXA4801