XTA apa-4e8 User manual

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CONTENTS
THANKS
THANKSTHANKS
THANKS ................................
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INTRODUCTION
INTRODUCTIONINTRODUCTION
INTRODUCTION ................................
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IMPORTANT SAFETY
IMPORTANT SAFETY IMPORTANT SAFETY
IMPORTANT SAFETY INSTRUCTIONS
INSTRUCTIONSINSTRUCTIONS
INSTRUCTIONS ................................
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INSTRUCTIONS DE SECU
INSTRUCTIONS DE SECUINSTRUCTIONS DE SECU
INSTRUCTIONS DE SECURITE IMPORTANTES
RITE IMPORTANTESRITE IMPORTANTES
RITE IMPORTANTES ................................
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DECLARATION OF CONFO
DECLARATION OF CONFODECLARATION OF CONFO
DECLARATION OF CONFORMITY
RMITYRMITY
RMITY ................................
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1010
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INSTALLING YOUR APA:
INSTALLING YOUR APA:INSTALLING YOUR APA:
INSTALLING YOUR APA: ................................
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1111
11
Unpac ing 11
Electrical Considerations 12
Mechanical Considerations 13
CONNECTING TO YOUR A
CONNECTING TO YOUR ACONNECTING TO YOUR A
CONNECTING TO YOUR APA:
PA:PA:
PA: ................................
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1414
14
Audio Inputs Wiring 14
RS485 Output Wiring 14
Spea er Outputs Wiring 15
GETTING TO KNOW YOUR
GETTING TO KNOW YOURGETTING TO KNOW YOUR
GETTING TO KNOW YOUR APA:
APA:APA:
APA: ................................
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1616
16
Front Panel Layout and Controls 16
Rear Panel Controls and Soc ets 18
Rear Panel Status LED Groups 19
GPIO Connections 19
Signal Paths and Bloc Diagram 20
Input Sources 21
AES Inputs 21
Pre-Matrix Processing 22
Processed Input Channel Bloc s 23
Mix Matrix to Power Amp Processing Channels / Networ Outputs 24
Power Amp Channels Processing Bloc s 25

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OPERATING YOUR APA:
OPERATING YOUR APA:OPERATING YOUR APA:
OPERATING YOUR APA: ................................
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2727
27
Powering Up 27
Powering Down and Returning Home 28
Home Screen Layout 29
The “Monochrome Concept” 29
User Metrics 30
ncoming Mains Monitor 30
Amplifier Temperatures 31
Quick nputs Monitor 32
Amp Channel Loads 33
Auto Scrolling of User Metrics 34
Tri Colour Panel Metering 35
Output Channel Menu 36
Overview 36
Quick Gain Trim 36
Output Preset 37
Limiter Threshold 37
Output Polarity (Phase Reverse) 37
System Menu 38
Overview 38
UNDERSTANDING YOUR A
UNDERSTANDING YOUR AUNDERSTANDING YOUR A
UNDERSTANDING YOUR APA
PAPA
PA ................................
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3939
39
Memories, Presets and File Structures 39
nternal SD Card 39
USB Flash Drives: Firmware Upgrades and Presets/Memories 39
The Concept of File Syncing 41
Recalling Unit Memories 42
Upgrading Firmware via USB 44
Mains RMS Current Limiter 47
Identify Unit 48
Default Audio 48
Default User Settings 49
Emergency Voice Evacuation Playbac 50
System Security 51
Overview and Locking Procedure 51
Forgotten Your Password? 51
SYSTEM WARNINGS
SYSTEM WARNINGSSYSTEM WARNINGS
SYSTEM WARNINGS ................................
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5252
52

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REMOTE CONNECTION TO
REMOTE CONNECTION TOREMOTE CONNECTION TO
REMOTE CONNECTION TO YOUR APA
YOUR APAYOUR APA
YOUR APA ................................
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5454
54
Overview 54
Connect to a Network 54
Adhoc Connections (no DHCP Server) 55
Manual (fixed) P Address Selection 55
LOOKING AFTER YOUR A
LOOKING AFTER YOUR ALOOKING AFTER YOUR A
LOOKING AFTER YOUR APA:
PA:PA:
PA: ................................
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5757
57
Maintenance 57
Warranty 57
PERFORMANCE OF YOUR
PERFORMANCE OF YOUR PERFORMANCE OF YOUR
PERFORMANCE OF YOUR APA:
APA:APA:
APA: ................................
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5858
58
Technical Specifications 58
General 58
Audio System 58
Digital Audio 59
Storage & Losses 59
Physical and Mechanical 59
nput Power 60
Output Power: Peak Performance 60
Output Power: Continuous Performance 61
Power Measurement Test Types 62
Test type 1: Continuous RMS Sine Wave 62
Test type 2: Continuous Pink Noise 62
Test type 3: Short Burst Sine Wave 62
Test type 4: Long Burst Sine Wave 62

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ADDITIONAL INFORMATI
ADDITIONAL INFORMATIADDITIONAL INFORMATI
ADDITIONAL INFORMATION ABOUT YOUR APA:
ON ABOUT YOUR APA:ON ABOUT YOUR APA:
ON ABOUT YOUR APA: ................................
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6363
63
Appendix I: Dynamic EQ 63
Mode : “Cut Above” 63
Mode : “Cut Below” 64
Mode : “Boost Above” 65
Mode V: “Boost Below” 66
Appendix II: Program Limiter and Pea Limiter 67
Program Limiter 67
Peak Limiter 68
Setting Accurate Limiter Thresholds — Program Limiter 70
Setting Accurate Limiter Thresholds — Peak Limiter 71
Setting Appropriate Attack and Release Times 71
Appendix III: Parametric Filter Types and Uses 72
Standard Parametric EQ 72
High/Low Shelving EQ 73
Creating a Flat-topped EQ Response 73
Bandpass Filter 74
Notch Filter 74
All Pass Filter 75
Phase Filter 75
Low/High Pass Variable ‘Q’ Filter 76

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Than s
Than sThan s
Than s
Thank you for choosing the APA-4E8 adaptive processing amplifier for your application.
Please spend a little time reading through this manual, so that you obtain the best possible
performance from the unit and become familiar with its operating requirements.
All XTA products are carefully designed and engineered for cutting-edge performance and
world-class reliability. f you would like further information about this or any other XTA
product, please contact us.
We wish you many years of flawless service from this unit and look forward to hearing from
you in the near future.
I
II
Introduction
ntroductionntroduction
ntroduction
The APA Series — Adaptive Processing Amplification — are four channel Class D amplifiers
with extensive processing, connectivity and control capabilities. The new power and DSP
platforms have been designed to interact intelligently and adapt to prevailing conditions,
protecting drivers, and significantly enhancing performance from all speaker systems.
The power stages and processing tightly integrate with the power supply featuring 96k
analogue to digital converters not only on the analogue inputs but also directly at the speaker
outputs, monitoring voltage and current. nputs and outputs are simultaneously being
processed by the DSP, along with data about the mains supply, allowing the APA to adapt and
correct to keep your music sounding better than ever.
n addition to this adaptive processing, you still have full control over a powerful suite of
filtering and protection, including multiple bands of our legendary dynamic EQ, F R filtering
and phase linearisation, ultra-transparent compression and limiting, plus all the classic
crossover and EQ components traditionally used to set up your system.
Add to this a fully flexible matrix with the ability to source audio either locally from AES or
analogue inputs, or via a networked audio connection (Dante/AVB). With native Mac and PC
remote software also available, you’ll understand why we don’t think this is just an amplifier
with some DSP built in…

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Import
ImportImport
Important Safety Instructions
ant Safety Instructionsant Safety Instructions
ant Safety Instructions
CAUT ON: R SK OF ELECTR C SHOCK.
DO NOT OPEN
WARN NG: Apparatus with CLASS construction shall be connected to a MA NS socket outlet with a protective
earthing connection.
WARN NG: To prevent injury, this apparatus must be securely attached to the rack in accordance with the
installation instructions.
1.
Read these instructions.
2. Keep these instructions.
3. Heed all warnings.
4. Follow all instructions.
5. Do not use this apparatus near water.
6. Clean only with a dry cloth.
7. Do not block any ventilation openings, install in
accordance with the manufacturer’s instructions.
8. Do not install near any heat sources, such as
radiators, heat registers, stoves or other apparatus
(including amplifiers) that produce heat.
9. Do not defeat the safety purpose of the polarized or
grounding-type plug. A polarized plug has two blades
with one wider than the other. A grounding-type plug
has two blades and a third grounding prong. The wide
blade or the third prong are provided for your safety. f
the provided plug does not fit into your outlet, consult
an electrician for replacement of the obsolete outlet.
10. Protect the power cord from being walked on or
pinched particularly at plugs, convenience
receptacles and the point where they exit from the
apparatus.
11. Only use attachments/accessories specified by the
manufacturer.
12. Use only with the cart, tripod, bracket or table
specified by the manufacturer, or sold with the
apparatus. When a cart is used, use caution when
moving the cart/apparatus combination to avoid injury
from a tip over.
13. Unplug this apparatus during lightning storms or
when unused for a long period of time.
14. Refer all servicing to qualified service personnel.
Servicing is required when the apparatus has been
damaged in any way, such as if the power-supply cord or
plug is damaged, liquid has been spilled or objects have
fallen into the apparatus, the apparatus has been
exposed to rain or moisture, does not operate normally,
or has been dropped.
15. Do not expose this equipment to dripping or
splashing and ensure that no objects filled with liquids,
such as vases, are placed on the equipment.
16. To completely disconnect this equipment from the
AC mains, disconnect the power cord from the mains
circuit breaker.
17. This unit is fitted with a 3-wire power cord. For
safety reasons, THE EARTH LEAD SHOULD NOT BE
D SCONNECTED N ANY C RCUMSTANCE.
The lightning flash with arrowhead
symbol within an equilateral triangle is
intended to alert the user to the presence
0f uninsulated “dangerous voltage”
within the product’s enclosure that may
be of sufficient magnitude to constitute a
risk of electric shock to persons.
The exclamation mark within an
equilateral triangle is intended to alert
the user of important operating and
maintenance (servicing) instructions in
the literature accompanying the
appliance.

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Instructions De Securite Importantes
Instructions De Securite ImportantesInstructions De Securite Importantes
Instructions De Securite Importantes
ATTENT ON: R SQUE DE CHOC ELECTR QUE.
NE PAS OUVR R
ATTENT ON: Appareils de construction de CLASSE doit être raccordé au réseau électrique via une prise de courant
reliée à la terre.
ATTENT ON: Pour éviter toute blessure, cet appareil doit être solidement fixé à la torture, conformément aux
instructions d'installation.
1.
Lisez ces consignes.
2. Conservez ces consignes.
3. Respectez tous les avertissements.
4. Respectez toutes les consignes d’utilisation.
5. N’utilisez jamais l’appareil à proximité d’un liquide.
6. Nettoyez l’appareil avec un chiff on sec.
7. Veillez à ne pas empêcher la bonne ventilation de
l’appareil via ses ouïes de ventilation. Respectez les
consignes du fabricant concernant l’installation de
l’appareil.
8. Ne placez pas l’appareil à proximité d’une source
de chaleur telle qu’un chauff age, une cuisinière ou
tout appareil dégageant de la chaleur (y compris un
ampli de puissance).
9. Ne supprimez jamais la sécurité des prises
bipolaires ou des prises terre. Les prises bipolaires
possèdent deux contacts de largeur diff érente. Le
plus large est le contact de sécurité. Les prises terre
possèdent deux contacts plus une mise à la terre
servant de sécurité. Si la prise du bloc d’alimentation
ou du cordon d’ali-mentation fourni ne correspond
pas à celles de votre installation électrique, faites
appel à un électricien pour eff ectuer le changement
de prise.
10. nstallez le cordon d’alimentation de telle façon
que personne ne puisse marcher dessus et qu’il soit
protégé d’arêtes coupantes. Assurez-vous que le
cordon d’alimentation est suffisamment protégé,
notamment au niveau de sa prise électrique et de
l’endroit où il est relié à l’appareil; cela est également
valable pour une éventuelle rallonge électrique.
11. Utilisez exclusivement des accessoires et des
appareils supplémentaires recommandés par le
fabricant.
12.
Utilisez exclusivement des chariots, des diables, des
présentoirs, des pieds et des surfaces de travail
recommandés par le fabricant ou livrés avec le produit.
Déplacez précautionneusement tout chariot ou diable
chargé pour éviter d’éventuelles blessures en cas de
chute.
13. Débranchez l’appareil de la tension secteur en cas
d’orage ou si l’appareil reste inutilisé pendant une
longue période de temps.
14. Les travaux d’entretien de l’appareil doivent être eff
ectués uniquement par du personnel qualifié. Aucun
entretien n’est nécessaire sauf si l’appareil est
endommagé de quelque façon que ce soit (dommages
sur le cordon d’alimentation ou la prise par exemple), si
un liquide ou un objet a pénétré à l’intérieur du châssis,
si l’appareil a été exposé à la pluie ou à l’humidité, s’il
ne fonctionne pas correctement ou à la suite d’une
chute.
15. N'exposez pas cet équipement au fait de tomber
goutte à goutte ou au fait d'éclabousser et garantissez
qu'aucun objet rempli des liquides, comme les vases,
n'est placé sur l'équipement.
16. Pour complètement débrancher cet équipement de
la conduite principale de courant alternatif, débranchez
la corde de pouvoir du disjoncteur de conduite
principale.
17. Cette unité est correspondue avec une corde de
pouvoir de 3 fils. Pour les raisons de sécurité, L'AVANCE
DE TERRE NE DEVRA T ÊTRE DÉBRANCHÉE DANS
AUCUNE C RCONSTANCE.
Le symbole repr
é
sentant un éclai
r fl
é
ch
é
dans un triangle équilatéral a pour but
d’alerter l’utilisateur de la présence
d’une “tension dangeruese” non isolée à
l’intérieur du boitier, pouvant être d’une
force suffisante pour constituer un risqué
d’électrocution.
Le point
d’exclamation dans un triangle
équilat é ral a pour but d’alerter
l’untilisateur de la présence
d’instructions importantes concernant le
fonctionnement et la maintenance, dans
la documentation qui accompagne
l’appariel.

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Declaration Of Conformity
Declaration Of ConformityDeclaration Of Conformity
Declaration Of Conformity
We, the manufacturer:
XTA Electronics Limited,
The Design House
Vale Business Par
Worcester Road
Stourport on Severn
Worcestershire
England
DY13 9BZ
acknowledge our responsibility that the following products:
Kind of equipment: Audio Amplifier
Commodity Code: 8518408990
Type Designation: APA-4E8
is manufactured:
in accordance with EMC Directive 2004/108/EC,
in compliance with the following norm(s) or document(s):
Technical Regulations: EN55103-1:1996, EN55103-2:1996
and
in accordance with the Low Voltage Directive 2006/95/EC,
in compliance with the following norm(s) or document(s):
Technical Regulations: EN/IEC60065:2002 7
th
Edition
Signed: ……………………………………………………………………
Name: Alex Cooper
Position: Research and Development Manager
Date: May 2015

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Installing your
Installing your Installing your
Installing your APA
APAAPA
APA:
::
:
Unpac ing
After unpacking the unit, please check it carefully for any damage. f any is found,
immediately notify the carrier concerned - you, the consignee, must instigate any claim.
Please retain all packaging in case of future re-shipment.
THIS WAY UP
Th e Des ign House
Vale Bu sin ess P ark
Worcest er R oad
Stou rpo rt on Seve rn
Worcs.
En glan d
Tel +44 ( 0) 1 299 8 79 977
Fa x [phone]

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Installing Your APA:
Installing Your APA:Installing Your APA:
Installing Your APA:
Electrical Considerations
The amplifier is fitted with a universal power supply which will operate world-wide — no user
setting is required.
Make sure power outlets conform to the power requirements listed on the back of the unit.
Damage caused by connecting to improper AC voltage is not covered by the warranty.
SAFETY WARNING
Where a MA NS plug or appliance coupler is used as the disconnect device, it should remain
readily operable.
Where the amplifier is mounted in a rack and permanently connected to the mains, then the
rack should be installed with a readily accessible connector or an ALL POLE circuit breaker
with 3mm breaking distances.
For safety reasons,
THE EARTH LEAD SHOULD NOT BE DISCONNECTED IN ANY CIRCUMSTANCE.
f ground loops are encountered consult the section on connecting your amplifier on page 14.
The wiring colours are:
230V AREAS: EARTH = GREEN AND YELLOW 120V AREAS: EARTH = GREEN
NEUTRAL = BLUE NEUTRAL = WH TE
L VE = BROWN L VE = BLACK
DO NOT USE THE UN T F THE ELECTR CAL POWER CORD S 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 and the
point where they exit from the appliance.
ALWAYS OPERATE THE UN T W TH THE AC GROUND W RE CONNECTED TO THE ELECTR CAL
SYSTEM GROUND. Precautions should be taken so that the means of grounding of a piece of
equipment is not defeated.
DO NOT REMOVE THE L D. Removing the lid will expose you to potentially dangerous
voltages. There are no user serviceable parts inside.

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Installing Your APA:
Installing Your APA: Installing Your APA:
Installing Your APA:
Mechanical Considerations
To ensure that your APA performs to specification, it should be mounted in a suitable rack or
enclosure as described below. Like all high power amplifiers, it should be kept away from
other equipment which is sensitive to magnetic fields. Also, this amplifier may suffer a
substantial reduction in performance if it is subjected to, or mounted close to equipment
which radiates high RF fields.
Warning: To prevent injury, this apparatus must be securely attached to the rack in
accordance with the installation instructions.
When mounting the amplifier in a rack or enclosure:
Be aware that…
THE FRONT PANEL S NOT CAPABLE OF SUPPORT NG THE UN T ON TS OWN.
Make sure that the rear of the unit is adequately supported. The depth of the front panel
relative to the front of the rack may be adjusted by moving the side panel supports.
ENSURE THERE S ADEQUATE VENT LAT ON.
The cooling fans suck cool air in through the front and blow hot air out at the rear of the unit
through the ventilating grills. The front and rear of the amplifier should have free exposure to
the air (i.e. in a rack leave the front & rear doors off), with 2cm air gap at the sides.
F A R S NOT ALLOWED TO ESCAPE FROM THE REAR, OVER-HEAT NG W LL OCCUR.
Take care when mounting other equipment in the same rack.
Make sure that the rack unit has a separate earth connection (technical earth).
Please also see the notes regarding maintenance on page 57.

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Connecting To Your
Connecting To Your Connecting To Your
Connecting To Your APA
APAAPA
APA:
: :
:
Audio Inputs Wiring
nputs - The inputs are made via 3-pin XLR connectors, which are electronically balanced and
should be connected via a high grade twin core screened cable, as follows:
P N1: Screen (see NOTE)
P N2: Hot (signal +)
P N3: Cold (signal -)
The amplifier is designed to operate with fully balanced equipment and ground loops or loss
of performance may be experienced if connected to unbalanced sources. f it is unavoidable
however, the following wiring should be used. The cable should still be twin core plus screen.
P N1: Screen - connected to the chassis of the unbalanced equipment - or left disconnected
at the unbalanced end.
P N2: Hot (signal +)
P N3: Cold (ground 0V)
NOTE: This amplifier is wired to the latest industry recommendations. P N1 is connected
directly to the chassis/mains earth. f ground loops (mains hum) are encountered remove the
screen connection from the one end of the cable and leave it open circuit. f problems persist,
consult your dealer/supplier.
DO NOT TAMPER W TH OR ALTER ANY GROUND (EARTH) CONNECT ONS NS DE THE
AMPL F ER.
RS485 Output Wiring
The RS485 output is a data port for connection to other XTA equipment only. t is currently
not supported, however for reference, the following wiring should be used:
P N1: Screen (see NOTE)
P N2: Hot (signal +)
P N3: Cold (signal -)
X
L
R
F
E
M
A
L
E
X
L
R
M
A
L
E

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Spea er Outputs Wiring
The speaker outputs are via Neutrik Speakon connectors. 2 pole (NL2FC) or 4 pole (NL4FC)
connectors can be used.
Pin 1+: Hot
Pin 1-: Cold
Additionally Channel 1 Speakon connector carries Channel 2 output on Pins +2 & -2 to allow
easy bi-amping or bridged operation using a single NL4 connector.
Pin 2+: Hot Ch. 2
Pin 2-: Cold Ch. 2
n the same way, channel 3’s Speakon carries channel D on 2+ and 2-.
There must be no shared connections between channels.
The minimum load per single channel is 2 ohms. XTA recommend running channels with a
minimum 2.7 ohm load for maximum efficiency and long term power delivery (3 x 8 Ohm
loads in parallel).
As the currents involved are very high, and to ensure best performance, the speaker cables
should be kept as short as possible and conform to the following minimum requirements:
APA-4E8: 22 Amps into 4 Ohm speaker loads.
When operating the amplifier into loads of less than 4 Ohms, be aware that the current
capacity of the speaker cables will need to be increased above the values quoted above.
Do not connect the inputs/outputs to any other voltage source such as a battery, mains source
or power supply, regardless of whether the amplifier is turned on or off.
Do not run the output of any amplifier channel back into another channel’s input and do not
parallel or series-connect an amplifier output with any other amplifier output.
Connecting To Your Amplifier: Bridged (Mono) Operation
Use Channel 1 or 3 Output Speakon connector and connect as follows:
Pin 2+: Hot
Pin 1-: Cold
When operating in bridged mode, the minimum impedances are doubled.
The minimum load in bridged mode is 4 ohms.
S
P
E
A
K
O
N
N
L
2
&
N
L
4

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Getting To
Getting To Getting To
Getting To Know Your
Know YourKnow Your
Know Your APA
APAAPA
APA:
::
:
Front Panel Layout and Controls
1: USB ‘OTG’ Socket: APA works in Host mode, so USB memory sticks can be plugged in here
to update firmware, download presets, save log files, and upload EVAC playout messages.
Please see notes on page 39 for more information.
2: LCD Screen: This full colour display primarily operates in black and white, only showing
warnings in red — at a glance if you see no colour then you can be sure your APA is operating
normally!
3: Back and Next Navigation Keys: From the Home Screen, these will cycle through various
“User Metrics” detailing the amplifier’s performance and current status — please see page 29
for more information on the “User Metrics”. They are also used to navigate the main menu
system and output menus.
4: Velocity Sensitive Encoder: Used to alter parameter values, and may also be used to cycle
through “User Metrics” from the Home Screen.
5: Mute Keys: These will mute the output channel processing sections of the amplifier. They
do not affect input processing or audio sent back out on the network. Please refer to the
system block diagram on page 21 for more information.
6: Standby/Home Key: f illuminated RED then the amplifier is in standby (no display shown
but DSP is still active and amplifier is still available on the network). Press and hold for 3
seconds to power up. A three second press will also put the amplifier into standby. Use as a
quick “Exit” from any menu to get back to the Home Screen and User Metrics.
7: Output Edit Keys: These directly access output channel gains, as well as other output
related information such as limiter thresholds, polarity switching, and current preset
information.
8: Tri-colour metering: As all meter elements can display green, yellow or red, APA can
show many different things on the meters. Default meter mode shows output channel dB
from limit. More information on page 35.
9: Enter Key: Used to confirm selections and enter sub-menus where appropriate.
10: Menu Key: Press to access system wide parameters and specific sub-menus.

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Front Panel Layout and Controls cntd…
11: Status and Warning ndicators: Permanent indication of the following:
ALARM: lluminates to show any condition APA needs to warn you about —
the list of possible warnings is covered on page 52.
CTRL: lluminates when a connection is made from the CTRL (control)
Ethernet socket on the rear panel, to a valid network.
AUD1: lluminates when a connection is made from the AUD1 (audio)
Ethernet socket on the rear panel, to a valid network.
AUD2: lluminates when a connection is made from the AUD2 (audio)
Ethernet socket on the rear panel, to a valid network.
USB: lluminates when a USB stick is connected and data is being
transferred. Do not disconnect USB device if LED is flashing.
12: Air Vents: The amplifier draws air in from the front and exhausts from the back. Please
ensure there is adequate ventilation space front and back — see page 57 for more information
on looking after your amplifier.

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Rear Panel Controls and Soc ets
1: Mains nput Socket: Mains connection is via a 32A ”Powercon” type plug. Supply voltage is
100-240V AC. This unit must be earthed.
2: GP O Socket: Connections are via Phoenix “mini” connectors. They can be used to provide
feedback of fault conditions, as well as being used to trigger different amplifier events such
as mutes, standby, and emergency evacuation message playback. Please see page 19 for
more information on the current capabilities.
3: RS485 Output Socket: This socket is intended for connection to other XTA processors for
control data bridging from the Ethernet control port. t is not intended to be used as a
method of primary remote control of this amplifier. Please see page 14 for more information.
4: Comms Status LEDs: This group of 4 tricolour LEDs shows if the current Ethernet and
RS485 comms ports are connected and in use. More information on their various modes of
operation is given on page 19.
5: CTRL Ethernet Socket: This RJ45 socket connects the amplifier to a valid Ethernet
network for remote control and monitoring.
6: AUD1 & AUD2 Ethernet Sockets: This pair of RJ45 sockets connect the amplifier to a valid
Ethernet network for transmission of audio data.
7: nput Status LEDs: This group of 4 tricolour LEDs can show various information about
signal level or lock status in AES mode. Please see page 19 for more information.
8: Analogue and AES Digital nput Sockets: By default these four sockets are four analogue
inputs, but individual pairs of sockets can be switched (via remote software and memory
recall via the front panel) to receive AES digital audio. AES input on channel A’s XLR provides
a stereo stream designated AES A + AES B; AES input on channel C’s XLR provides a stereo
stream designated AES C + AES D. When an AES input is selected, the “other” channel of the
pair is disabled (you cannot input analogue into channel B XLR if A&B are set to AES mode).
9: Speaker Output Sockets 1&2: The primary speaker outputs are via Neutrik Speakon
connectors on 1+ and 1-. Two pole (NL2FC) or four pole (NL4FC) connectors can be used.
Additionally Channel 1 Speakon connector carries Channel 2 output on Pins +2 & -2 to allow
easy bi-amping or bridged operation using a single NL4 connector.
10: Speaker Output Sockets 3&4: The primary speaker outputs are via Neutrik Speakon
connectors on 1+ and 1-. Two pole (NL2FC) or four pole (NL4FC) connectors can be used.
Additionally Channel 3 Speakon connector carries Channel 4 output on Pins +2 & -2 to allow
easy bi-amping or bridged operation using a single NL4 connector.

APA-4E8 Operator’s Manual Page 19
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Rear Panel Status LED Groups
There are two sets of status LEDs on the rear panel — one set beside the input XLR sockets
and one set beside the network sockets. Both sets are tri-colour LEDS and so can show a
variety of information using colour and steady/flashing indication as explained below.
The input status LEDs show both analogue signal preset and approaching clipping point, and
AES lock status and sample rate.
n analogue input mode, the corresponding input channel’s LED will be off in the absence of
signal and will show signal present in green and 1dB below clip in red.
nput level too high — above +18dBu and approaching clipping point of input!
Analogue signal present above -60dBu — all OK
No analogue signal present, or below -60dBu
n AES input, indicators for inputs A and C will show digital input status and sample rate. The
choice of AES or analogue may be selected remotely on a pair-by-pair basis, so A&B can still
be showing analogue level , with C showing digital status for the C&D AES stream, and vice
versa.
Flashing red — AES input active, no signal lock (so no audio!)
Steady red — locked to 48k AES stream
Steady yellow — locked to 96k AES stream (ideal)
Steady green — locked to 192k AES stream
GPIO Connections
The amplifier is equipped with a 10 way mini-Phoenix type connector that offers a pair of logic
level inputs for triggering different aspects of APA’s operation, and a pair of logic level
outputs for simple remote reporting on various statuses.
t is wired as follows:
1: 3V3 OUTPUT
2/3: SO 1 OUT +/-
4/5: SO 2 OUT +/-
6/7: SO 1 N +/-
8/9: SO 2 N +/-
10: CHASS S GND
Currently emergency wav file playback from the SD card is offered, but this feature set will be
enriched in later firmware releases. Please see the section about the SD card file structure
and wav file format on page 39.

Page 20 APA-4E8 Operator’s Manual
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Signal Paths and Bloc Diagram