Alesis RA500, RA300, RA150 User Manual

REFERENCE SERIES

POWER AMPLIFIERS

REFERENCE MANUAL

™

™

™

©2000 Alesis Corporation

Alesis RA150-500 Reference Manual

© Copyright 2000, Alesis Studio Electronics, Inc. All rights reserved. Reproduction in whole or in part is
prohibited. “RA150/300/500” and “Reference Series” are trademarks of Alesis Studio Electronics, Inc.

ALESIS CONTACT INFORMATION

Alesis Studio Electronics, Inc.
1633 26th Street
Santa Monica, CA 90404
USA

Do not use this address for repair service.

Telephone: 800-5-ALESIS (800-525-3747)
E-Mail: [e-mail]
Website: http://www.alesis.com

CONTENTS

Introduction......................................................2

How to Use This Manual...........................2

IMPORTANT SAFETY INSTRUCTIONS.... 3

Instructions de Sécurité Importantes (French)......4

Beim Benutzen dieses Produktes beachten Sie
bitte die folgenden Sicherheitshinweise:

(German) ..........................................................5

CE Declaration of Conformity.............................6

ABOUT THE RA150/300/500............. 7

Principal Features..............................................7

The Chassis..............................................7

Inputs and Outputs...................................7

Amplifier topology ...................................7

Protection Circuitry ..................................7

About this manual.............................................8

CONNECTIONS ................................... 9

Unpacking and Inspection..................................9

Power Considerations........................................9

The AC Cord and Grounding ....................9

120 Volt/230 Volt Operation.................... 10

Fuse....................................................... 10

Electrical Service to the RA150/300/500... 10

Operating Environment ...................................11

Temperature Considerations in Rack

Mounting...............................................11

Other Rack Mounting Tips ...................... 11

Mounting on a Shelf or in a Non-Rack

Enclosure............................................... 12

Avoiding Electromagnetic Interference .... 12

Inputs ............................................................. 13

Input Jack Characteristics........................ 13

Cables.................................................... 15

Cable Wiring Tips................................... 15

Balanced or Unbalanced? ........................16

Outputs .......................................................... 18

What's the Load Impedance?................... 18

Connectors..............................................18

Speaker Cables........................................18

Connecting Speaker Cables to Binding

Posts.......................................................19

The Importance of Speaker Polarity..........20

Output Connections for Bridged

Operation ...............................................20

OPERATION......................................21

Front Panel Controls.........................................21

Volume Controls.....................................21

On-Off Switch.........................................21

Mute Switch............................................21

Protect/Clip Indicators............................22

Meters (RA300 and RA500 only)...............22

Back Panel Controls..........................................22

AC Voltage Switch ..................................22

Stereo/Bridged Mono Switch...................22

Checking For Proper Polarity............................22

Using the RA150 as a Headphone Amplifier.......23

Choosing the Correct Speakers..........................23

About Ground Loops........................................24

System Setup and Testing .................................25

Setting the Gain Properly.........................25

Output Relays/Thermal Cycling ..............26

TROUBLESHOOTING.......................... 27

Troubleshooting Index......................................27

Care and Maintenance......................................28

Cleaning.................................................28

Refer All Servicing to Alesis.....................28

Obtaining Repair Service .........................29

Customers outside the USA and

Canada: ..................................................29

SPECIFICATIONS...............................30

I

NDEX.............................................34

A

LESIS LIMITED WARRANTY ............ 35

RA150/300/500 Reference Manual 1

Introduction/Safety Instructions

INTRODUCTION

Thank you for purchasing this Alesis RA150, RA300,
or RA500™ Reference Series power amplifier. To
take full advantage of this amplifier’s functions, and
to enjoy long and trouble-free use, please read this
user’s manual carefully.

HOW TO USE THIS MANUAL

This manual is divided into the following
sections describing the various functions and
applications for the RA series amplifier. Though
we recommend you take time to read through
the entire manual once carefully, those having
general knowledge about amplifiers should use
the table of contents to look up specific
functions.

Chapter 1: Introduction. If you want to start
using the RA150/300/500 right away, here’s a
one-page guide to hooking it up and trying it
out.

Chapter 2: Connections. This chapter gives

detailed instructions for connecting the
RA150/300/500 to a variety of typical sound
systems.

Chapter 3: Operation. This section explains
how to run the Reference Series Amplifier
properly.

Chapter 4: Troubleshooting. This chapter
contains troubleshooting tips and service
information should problems occur.

When something important appears in

the manual, an icon (like the one on
the left) will appear in the left margin.
This symbol indicates that this
information is vital when operating
the RA150/300/500.

2 RA150/300/500 Reference Manual

Introduction/Safety Instructions

IMPORTANT SAFETY INSTRUCTIONS

SAFETY SYMBOLS USED IN THIS PRODUCT

This symbol alerts the user that there
are important operating and maintenance
instructions in the literature accompanying this
unit.

This symbol warns the user of
uninsulated voltage within the unit that can cause
dangerous electric shocks.

This symbol warns the user that output
connectors contain voltages that can cause
dangerous electrical shock.

PLEASE FOLLOW THESE PRECAUTIONS

WHEN USING THIS PRODUCT:

1. Read these instructions.

2. Keep these instructions.

3. Heed all warnings.

11. Unplug this apparatus during lightning storms
or when unused for long periods of time.

12. 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.
When the provided plug does not fit into
your outlet, consult an electrician for
replacement of the obsolete outlet.

13. Use only with a cart, stand, bracket, or table
designed for use with professional audio or

music equipment. In any installation,
make sure that injury or damage will not
result from cables pulling on the apparatus
and its mounting. If a cart is used, use
caution when moving the cart/apparatus

combination to avoid injury from tip-over.

4. Follow all instructions.

5. Do not use this apparatus near water.

6. Clean only with a damp cloth. Do not spray
any liquid cleaner onto the faceplate, as this
may damage the front panel controls or cause a
dangerous condition.

7. Do not block any of the 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. Protect the power cord from being walked on or
pinched, particularly at plugs, convenience
receptacles, and the point where they exit from
the apparatus.

10. Use only attachments or accessories specified by
the manufacturer.

RA150/300/500 Reference Manual 3

14. Refer all servicing to qualified service
personnel. Servicing is required when the
apparatus has been damaged in any way, such
as when 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. This unit produces heat when operated
normally. Operate in a well-ventilated area
with at least six inches of clearance from
peripheral equipment.

16. This product, in combination with an amplifier
and headphones or speakers, may be capable of
producing sound levels that could cause
permanent hearing loss. Do not operate for a
long period of time at a high volume level or at
a level that is uncomfortable. If you experience
any hearing loss or ringing in the ears, you
should consult an audiologist.

Introduction/Safety Instructions

INSTRUCTIONS DE SÉCURITÉ IMPORTANTES (FRENCH)

SYMBOLES UTILISÉS DANS CE PRODUIT

Ce symbole alèrte l’utilisateur qu’il
existe des instructions de fonctionnement et de
maintenance dans la documentation jointe avec ce
produit.

Ce symbole avertit l’utilisateur de la
présence d’une tension non isolée à l’intérieur de
l’appareil pouvant engendrer des chocs électriques.

Ce symbole prévient l'utilisateur de la
présence de tensions sur les raccordements de
sorties, représentant un risque d'électrocution.

VEUILLEZ SUIVRE CES PRÉCAUTIONS LORS

DE L’UTILISATION DE L’APPAREIL:

8. Ne pas installer à proximilé de sources de chaleur
comme radiateurs, cuisinière ou autre appareils
(don’t les amplificateurs) produisant de la
chaleur.

9. Ne pas enlever la prise de terre du cordon
secteur. Une prise murale avec terre deux
broches et une troisièrme reliée à la terre. Cette
dernière est présente pour votre sécurité. Si le
cordon secteur ne rentre pas dans la prise de
courant, demandez à un électricien qualifié de
remplacer la prise.

10. Evitez de marcher sur le cordon secteur ou de le
pincer, en particulier au niveau de la prise, et aux
endroits où il sor de l’appareil.

11. N’utilisez que des accessoires spécifiés par le
constructeur.

12. N’utilisez qu’avec un stand, ou table conçus pour
l’utilisation d’audio professionnel ou instruments
de musique. Dans toute installation, veillez de ne
rien endommager à cause de câbles qui tirent sur
des appareils et leur support.

1. Lisez ces instructions.

2. Gardez ces instructions.

3. Tenez compte de tous les avertissements.

4. Suivez toutes les instructions.

5. N’utilisez pas cet allareil à proximité de l’eau.

6. Ne nettoyez qu’avec un chiffon humide. Il est
potentiellement dangereux d'utiliser des
pulvérisateurs ou nettoyants liquides sur cet appareil.

7. Installez selon les recommandations du constructeur.

13. Débranchez l’appareil lors d’un orage ou lorsqu’il
n’est pas utilisé pendant longtemps.

14. Faites réparer par un personnel qualifié. Une
réparation est nécessaire lorsque l’appareil a été
endommagé de quelque sorte que ce soit, par
exemple losrque le cordon secteur ou la prise
sont endommagés, si du liquide a coulé ou des
objets se sont introduits dans l’appareil, si celui-ci
a été exposé à la pluie ou à l’humidité, ne
fonctionne pas normalement ou est tombé.

15. Puisque son fonctionement normale génère de la
chaleur, placez cet appareil au moins 15cm. des
équipments péripheriques et assurez que
l’emplacement permet la circulation de l’air.

16. Ce produit, utilisé avec un amplificateur et un
casque ou des enceintes, est capable de produite
des niveaux sonores pouvant engendrer une
perte permanente de l’ouïe. Ne l’utilisez pas
pendant longtemps à un niveau sonore élevé ou à
un niveau non confortable. Si vous remarquez
une perte de l’ouïe ou un bourdonnement dans
les oreilles, consultez un spécialiste.

4 RA150/300/500 Reference Manual

Introduction/Safety Instructions

BEIM BENUTZEN DIESES PRODUKTES BEACHTEN SIE BITTE DIE

FOLGENDEN

1. Lesen Sie die Hinweise.

2. Halten Sie sich an die Anleitung.

3. Beachten Sie alle Warnungen.

4. Beachten Sie alle Hinweise.

5. Bringen Sie das Gerät nie mit Wasser in
Berührung.

6. Verwenden Sie zur Reinigung nur ein
weiches Tuch. Verwenden Sie keine
flüssigen Reinigungsmittel. Dies kann
gefährliche Folgen haben.

7. Halten Sie sich beim Aufbau des Gerätes an
die Angaben des Herstellers.

8. Stellen Sie das Gerät nich in der Nähe von
Heizkörpern, Heizungsklappen oder
anderen Wärmequellen (einschließlich
Verstärkern) auf.

9. Verlegen Sie das Netzkabel des Gerätes
niemals so, daß man darüber stolpern kann
oder daß es gequetscht wird.

SICHERHEITSHINWEISE: (GERMAN)

und deshalb nicht mehr normal arbeitet
oder heruntergefallen ist.

14. Dieses Gerät produziert auch im
normalen Betrieb Wärme. Achten Sie
deshalb auf ausreichende Lüftung mit
mindestens 15 cm Abstand von anderen
Geräten.

15. Dieses Produkt kann in Verbindung mit
einem Verstärker und Kopfhörern oder
Lautsprechern Lautstärkepegel
erzeugen, die anhaltende Gehörschäden
verursachen. Betreiben Sie es nicht über
längere Zeit mit hoher Lautstärke oder
einem Pegel, der Ihnen unangenehm is.
Wenn Sie ein Nachlassen des Gehörs
oder ein Klingeln in den Ohren
feststellen, sollten Sie einen Ohrenarzt
aufsuchen.

10. Benutzen Sie nur das vom Hersteller
empfohlene Zubehör.

11. Verwenden Sie ausschließlich Wagen,
Ständer, oder Tische, die speziell für
professionelle Audio- und
Musikinstrumente geeignet sind. Achten
Sie immer darauf, daß die jeweiligen Geräte
sicher installiert sind, um Schäden und
Verletzungen zu vermeiden. Wenn Sie
einen Rollwagen benutzen, achten Sie
darauf, das dieser nicht umkippt, um
Verletzungen auszuschließen.

12. Ziehen Sie während eines Gewitters oder
wenn Sie das Gerät über einen längeren
Zeitraum nicht benutzen den Netzstecher
aus der Steckdose.

13. Die Wartung sollte nur durch qualifiziertes
Fachpersonal erfolgen. Die Wartung wird
notwendig, wenn das Gerät beschädigt
wurde oder aber das Stromkabel oder der
Stecker, Gegenstände oder Flüssigkeit in
das Gerät gelangt sind, das Gerät dem
Regen oder Feuchtigkeit ausgesetzt war

RA150/300/500 Reference Manual 5

Introduction/Safety Instructions

CE DECLARATION OF CONFORMITY

Manufacturer’s Name: Alesis Corporation

Manufacturer’s Address: 1633 26th Street

Santa Monica, CA 90404
USA

declares, that the product:

Product Name: RA150/300/500

Model Type: Audio amplifier

conforms to the following Standards:

Safety: EN60065

EMC: EN55103:1997 Class B

(all tests were performed with fully- shielded cabling.)

European Contact: Sound Technology

17 Letchworth Point, Letchworth,
Hertfordshire, SG6 1ND, England.
Phone: [phone]
Fax: [phone]

October 2000

6 RA150/300/500 Reference Manual

Chapter 1: Introduction

CHAPTER 1

ABOUT THE RA150/300/500

PRINCIPAL FEATURES

Please remember that a power amplifier
is a high-current, high-power device and
should be treated with respect and care.
Even if you are an audio veteran, we
urge you to read the entire manual to
make the best use of the RA150/300/500.

Thank you for purchasing an Alesis Reference
Series power amplifier, one of the most advanced
and highest value amplifiers available.

The Alesis models RA150, RA300, and RA500
provide extremely accurate sonic quality as well as
measured specifications, but their conservative
design and careful attention to electronic protection
means they will continue to operate at top condition
without special attention, year after year.

THE CHASSIS

plugs. A recessed rear panel switch allows easy
selection of stereo or bridged monaural operating
modes. AC power entry is via a detachable,
grounded IEC connector cable.

AMPLIFIER TOPOLOGY

The amplifier sections of the Reference Series utilize
a direct coupled, fully complementary circuit
topology. The input stages are a dual differential
type with active current sources. Output from the
differential amplifiers are coupled to balanced level
shifters operating on isolated boost rails for
improved efficiency and higher performance. These
stages then drive discrete, high current, triple
darlington output stages, fully rated for continuous
4 ohm operation with 2 ohm dynamic stability
(stereo mode only). The output stages are biased for
class AB operation. Emphasis is placed on
maintaining wide bandwidth, linearity and stability
under all operating conditions. An active DC servo
circuit is employed to automatically null DC output
voltage offsets. All models feature bridged mono
operation.

The Alesis Reference Series amplifiers are
constructed on rugged, heavy gauge steel chassis.
All units feature rack mount faceplates. For
maximum reliability and low-noise operation the
amplifiers use convection cooling with massive
extruded aluminum heat-sinks for reliable
operation under all ambient and load conditions.
The design of the external chassis protects rear
panel connectors (except RA 150). All models
feature detented front panel input level controls,
and overload/protect indicators. The RA300 and
RA500 amplifiers incorporate bar graph LED power
metering.

INPUTS AND OUTPUTS

The input sections of the amplifiers utilize precision
electronically-balanced input circuitry for low noise
balanced input operation. All units have 1/4”
balanced TRS input connectors. The RA300 and
RA500 also have XLR connectors. Unbalanced RCA
(phono) style input connectors are also used. The
output connectors are industry-standard, heavy­duty dual binding posts, which can accept large
diameter wire or 3/4" (19 mm) spaced dual banana

PROTECTION CIRCUITRY

Protection for the amplifier consists of active
circuitry that continuously monitors the output
stage for excessive DC offset, short circuits and
thermal overload. In the event of an output fault,
the protection circuitry will activate the output relay
and disconnect the loudspeaker load. This circuitry
will also mute the amplifier during power on/off
transitions.

The power supplies of the amplifiers utilize heavy­duty stacked steel EI laminated transformers for
maximum performance and reliability. High current
bridge rectifiers, massive secondary capacitors and
current in-rush limiters are used in all models. All
models are designed for 120/230-volt operation
with an external voltage selection switch.

All components are of high quality and mechanical
construction and are optimized for high reliability
under adverse physical and electrical conditions.

RA150/300/500 Reference Manual 7

Introduction: Chapter 1

Reference Series Features-

• DC coupled, fully complementary discrete
amplifier topology

• Actively biased, dual differential input
stages

• Wide bandwidth, low distortion design

• Fully protected from all fault conditions

• LED output level metering (RA 300, RA

500)

• Front panel level controls

• Overload/Fault indicators

• Bridged mono operation

• Balanced 1/4” & RCA single-ended input

connectors

• XLR input connectors (RA 300, RA 500)

• Heavy-duty, dual binding post output

connectors

• Relay-controlled turn on/off

ABOUT THIS MANUAL

In most respects, the three different amplifiers
covered by this manual are similar except for their
power ratings. Operational differences will be
noted individually.

• Silent, convection-cooled design

• Heavy-duty steel chassis

8 RA150/300/500 Reference Manual

Chapter 2: Connections

CHAPTER 2

CONNECTIONS

UNPACKING AND INSPECTION

Your Alesis RA150/300/500 was carefully packed
at the factory, and the shipping carton was designed
to protect the unit during shipping. Do not discard
the packing materials; they may be helpful in the
unlikely event that you need to return your
RA150/300/500 for servicing, or for transporting
the amplifier when it is not mounted in a rack or
other enclosure.

The shipping carton should contain the following
items:

• RA150/300/500 amplifier

• This instruction manual

• Power cable

• Alesis Warranty card

It is important to register your purchase;
if you have not already filled out your
warranty card and mailed it back to
Alesis, please take the time to do so now.

POWER CONSIDERATIONS

THE AC CORD AND GROUNDING

The RA150/300/500’s IEC-spec AC cord (do not
substitute any other type of AC cord) is designed to
connect to an outlet that includes three pins, with
the third, round pin connected to ground ("earth").
The ground connection is an important safety
feature designed to keep the chassis of electronic
devices such as the RA150/300/500 at ground
potential. Unfortunately, the presence of a ground
contact in an AC socket does not always indicate
that an outlet is properly grounded. Use an AC line
tester to determine this. If the outlet is not
grounded, consult with a licensed electrician.

The audio ground (pin 1 of the XLR, the sleeve of
the 1/4" jack) is not isolated from the chassis.

Tip: You don't have to use the provided 6-foot long

AC cord. Many electronic stores carry the
standard "NEMA-to-CEE" cable in lengths
from 6 inches to 20 feet. This is better than
wrapping the cord in a coil if it is too long, or
using extension cords if it is too short.

Carefully unpack the amplifier and inspect it for
physical damage originating in shipping. If damage
is discovered and the amplifier was shipped to you,
immediately contact the transportation carrier and
make certain that the packing materials are
preserved for inspection. You as the consignee
must make any shipping claims; neither your dealer
nor Alesis can do this for you. If the amplifier was
not shipped to you, i.e. you picked it up from your
dealer, contact the dealer as soon as possible for
assistance.

RA150/300/500 Reference Manual 9

DO NOT OPERATE ANY ELECTRICAL
EQUIPMENT WITH UNGROUNDED
OUTLETS. PLUGGING THE RA150/300/500
INTO AN UNGROUNDED OUTLET, OR
“LIFTING” THE UNIT OFF GROUND WITH A
THREE-TO-TWO WIRE ADAPTER, CREATES
A HAZARDOUS CONDITION. ALESIS
CANNOT BE RESPONSIBLE FOR PROBLEMS
CAUSED BY USING THE RA150/300/500
OR ANY ASSOCIATED EQUIPMENT WITH
IMPROPER AC WIRING.

Connections: Chapter 2

120 VOLT/230 VOLT OPERATION

The Alesis Reference Series amplifiers feature dual­voltage operation. The AC input voltage is selected
by a recessed switch on the back panel. The tab is
recessed and a tool (small screw driver, pencil, pen,
etc.) is required to shift from 120-volt to 230-volt
operation. Units sold in areas with 120V power (as
in the United States) should come with the switch
already set to that position.

Before connecting the amplifier to AC
power for the first time, make sure that
this switch is set correctly for the country
you're using the amp in.

If you change the voltage when
travelling, you must also replace the
power fuse with the proper amperage
(see page 10) and obtain the proper
detachable IEC power cable for the
country.

ELECTRICAL SERVICE TO THE
RA150/300/500

One of the most important considerations for
proper installation and operation of a power
amplifier is the capacity of the circuit feeding the
AC mains voltage to the amplifier. If the line does
not have sufficient current and voltage capacity, the
amplifier may not be able to deliver its full rated
output, both steady state and peak, with the result
that the sound character can dramatically suffer. In
short, any amplifier will only sound good when
connected to adequate AC power.

The maximum audio output rating of each amp (200
watts bridged for the RA150 to 1000 watts bridged
for the RA500) does not represent the total AC
power consumption by the unit. The following
table shows the power consumption at rated output:

Model Rated AC

consumption

RA150 270 watts 390 watts
RA300 500 watts 650 watts
RA500 840 watts 1080 watts

Maximum
(peak)

FUSE

If the fuse blows, replace with a fuse of the correct
type only; use of any higher amperage value will
void the warranty. FUSES ARE FOR YOUR

PROTECTION—NEVER SUBSTITUTE A FUSE
OF A HIGHER RATING, OR BYPASS IT.

All fuses are the "Slo-Blo" type, sized at 5mm
diameter x 20mm:

Model 100-120 volt 220-240 volt

RA150 T3.15AL250V T1.6AL250V
RA300 T6.3AL250V T3.15AL250V
RA500 T10AL250V T5AL250V

The fuse will not blow unless the unit is
overstressed. Before replacing the fuse, correct the
condition that caused it to blow in the first place.

Note that in typical studio applications the
average power consumption will be much less.

When not being driven, current consumption is 30
watts or less. Under most circumstances, normal
household or commercial power outlets will be
adequate. (A standard 15-amp circuit is capable of
supplying 1800 watts.) However, peak power
consumption may momentarily be 100 to 200 watts
higher on transient peaks; if you're connecting a lot
of other equipment to the same circuit you should
plan for an extra 20% headroom to avoid blowing a
circuit breaker. Note that when multiple devices
are plugged into a single AC outlet, the possibility
of overheated connections can exist. Long AC
extension cables may also degrade the supply
power.

Electrical standards have taken enormous strides
toward increased safety over the past few decades
thanks to circuit breakers, ground fault interrupters,
and improved wiring and insulation materials.
Unfortunately, some clubs are situated in older
buildings whose wiring may not meet current safety
standards, or have wiring that has deteriorated over
the years. Make sure the circuit supplying power to
the RA150/300/500 can supply enough current to
run it properly. If the circuit has to supply other
high-powered consumption units such as

10 RA150/300/500 Reference Manual