IEC 60268-3:2018

IEC 60268-3 ®
Edition 5.0 2018-04
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Sound system equipment –
Part 3: Amplifiers
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.

IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
The stand-alone application for consulting the entire The world's leading online dictionary of electronic and
bibliographical information on IEC International Standards, electrical terms containing 21 000 terms and definitions in
Technical Specifications, Technical Reports and other English and French, with equivalent terms in 16 additional
documents. Available for PC, Mac OS, Android Tablets and languages. Also known as the International Electrotechnical
iPad. Vocabulary (IEV) online.

IEC publications search - webstore.iec.ch/advsearchform IEC Glossary - std.iec.ch/glossary
The advanced search enables to find IEC publications by a 67 000 electrotechnical terminology entries in English and
variety of criteria (reference number, text, technical French extracted from the Terms and Definitions clause of
committee,…). It also gives information on projects, replaced IEC publications issued since 2002. Some entries have been
and withdrawn publications. collected from earlier publications of IEC TC 37, 77, 86 and

CISPR.
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published IEC Customer Service Centre - webstore.iec.ch/csc
details all new publications released. Available online and If you wish to give us your feedback on this publication or
also once a month by email. need further assistance, please contact the Customer Service
Centre: sales@iec.ch.
IEC 60268-3 ®
Edition 5.0 2018-04
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Sound system equipment –
Part 3: Amplifiers
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.160.10 ISBN 978-2-8322-5644-2

– 2 – IEC 60268-3:2018 RLV  IEC 2018
CONTENTS
FOREWORD . 5
1 Scope . 7
2 Normative references . 7
3 Terms, definitions and rated values . 7
3.1 Terms and definitions . 8
3.2 Rated values . 8
4 Conditions . 9
4.1 Rated conditions and standard measuring conditions . 9
4.1.1 Overview . 9
4.1.2 Rated conditions . 10
4.1.3 Standard measuring conditions . 11
4.2 Other conditions. 11
5 Classes of operation . 11
6 Interchangeable parts . 12
7 Automatic controls . 12
8 Power supply . 12
9 Position of the volume controls . 12
10 Pre-conditioning for measurements . 13
11 Series of measurements . 13
12 Variable consumption apparatus . 13
13 Marking . 13
14 Operating environment . 14
15 Characteristics to be specified, and their methods of measurement . 14
15.1 Power supply characteristics . 14
15.1.1 Characteristics to be specified . 14
15.1.2 Method of measurement . 14
15.2 Tolerance of (long-term) power supply voltage variations . 15
15.2.1 Characteristic to be specified . 15
15.2.2 Methods of measurement . 15
15.3 Tolerance of power supply frequency variations . 16
15.3.1 Characteristics to be specified . 16
15.3.2 Methods of measurement . 16
15.4 Tolerance of power supply harmonics and ripple . 17
15.4.1 Characteristics to be specified . 17
15.4.2 Methods of measurement . 17
15.5 Input characteristics . 17
15.5.1 Rated source impedance, characteristic to be specified . 17
15.5.2 Input impedance . 17
15.5.3 Rated source e.m.f., characteristic to be specified . 19
15.5.4 Minimum source e.m.f. for rated distortion-limited output voltage . 19
15.6 Output characteristics . 20
15.6.1 Rated load impedance, characteristic to be specified . 20
15.6.2 Output source impedance . 20
15.6.3 Output voltage and power (distortion-limited) . 21
15.6.4 Maximum effective output power (distortion-limited at 10 %) . 22

15.6.5 Regulation . 23
15.6.6 Overload restoring time . 24
15.7 Limiting characteristics . 24
15.7.1 Overload source e.m.f. . 24
15.7.2 Short-term maximum output voltage and power . 25
15.7.3 Long-term maximum output voltage and power . 25
15.7.4 Temperature-limited output power . 26
15.8 Characteristics of protection circuits . 27
15.8.1 General . 27
15.8.2 Protection against potentially damaging combinations of output voltage
and current . 28
15.8.3 Characteristics of d.c. offset protection circuits . 29
15.9 Sustaining-time for rated (distortion-limited) output voltage or power . 30
15.9.1 General . 30
15.9.2 Characteristic to be specified . 31
15.9.3 Method of measurement . 31
15.10 Gain . 32
15.10.1 Voltage gain and e.m.f. gain . 32
15.10.2 Maximum e.m.f. gain . 32
15.10.3 Attenuation characteristic of the volume control . 32
15.10.4 Attenuation characteristic of balance controls for multi-channel
equipment. 33
15.11 Response . 33
15.11.1 Gain-frequency response . 33
15.11.2 Gain-limited effective frequency range . 34
15.11.3 Distortion-limited effective frequency range . 34
15.11.4 Phase-frequency response . 35
15.12 Amplitude non-linearity . 35
15.12.1 General . 35
15.12.2 Rated total harmonic distortion, characteristic to be specified . 35
15.12.3 Total harmonic distortion under standard measuring conditions . 35
15.12.4 Total harmonic distortion as a function of amplitude and frequency . 36
15.12.5 Harmonic distortion of the nth order under standard measuring
conditions . 37
15.12.6 Harmonic distortion of the nth order as a function of amplitude and
frequency . 38
15.12.7 Modulation distortion of the nth order (where n = 2 or n = 3) . 38
15.12.8 Difference-frequency distortion of the nth order (where n = 2 or n = 3) . 40
15.12.9 Dynamic intermodulation distortion (DIM) . 41
15.12.10 Total difference frequency distortion . 43
15.12.11 Weighted total harmonic distortion . 44
15.13 Noise . 45
15.13.1 Characteristic to be specified . 45
15.13.2 Method of measurement . 45
15.14 Hum . 46
15.14.1 General . 46
15.14.2 Characteristics to be specified . 46
15.14.3 Method of measurement . 47
15.15 Balanced inputs and outputs . 47
15.15.1 Balance of the input . 47

– 4 – IEC 60268-3:2018 RLV  IEC 2018
15.15.2 Overload (distortion-limited) peak-to-peak common-mode input voltage . 48
15.15.3 Balance of the output . 49
15.16 Cross-t
...

IEC 60268-3 ®
Edition 5.0 2018-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Sound system equipment –
Part 3: Amplifiers
Équipements pour systèmes électroacoustiques –
Partie 3: Amplificateurs
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie
et les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez
les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.

IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
The stand-alone application for consulting the entire The world's leading online dictionary of electronic and
bibliographical information on IEC International Standards, electrical terms containing 21 000 terms and definitions in
Technical Specifications, Technical Reports and other English and French, with equivalent terms in 16 additional
documents. Available for PC, Mac OS, Android Tablets and languages. Also known as the International Electrotechnical
iPad. Vocabulary (IEV) online.

IEC publications search - webstore.iec.ch/advsearchform IEC Glossary - std.iec.ch/glossary
The advanced search enables to find IEC publications by a 67 000 electrotechnical terminology entries in English and
variety of criteria (reference number, text, technical French extracted from the Terms and Definitions clause of
committee,…). It also gives information on projects, replaced IEC publications issued since 2002. Some entries have been
and withdrawn publications. collected from earlier publications of IEC TC 37, 77, 86 and

CISPR.
IEC Just Published - webstore.iec.ch/justpublished

Stay up to date on all new IEC publications. Just Published IEC Customer Service Centre - webstore.iec.ch/csc
details all new publications released. Available online and If you wish to give us your feedback on this publication or
also once a month by email. need further assistance, please contact the Customer Service
Centre: sales@iec.ch.
A propos de l'IEC
La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC
Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la
plus récente, un corrigendum ou amendement peut avoir été publié.

Catalogue IEC - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
Application autonome pour consulter tous les renseignements
Le premier dictionnaire en ligne de termes électroniques et
bibliographiques sur les Normes internationales,
électriques. Il contient 21 000 termes et définitions en anglais
Spécifications techniques, Rapports techniques et autres
et en français, ainsi que les termes équivalents dans 16
documents de l'IEC. Disponible pour PC, Mac OS, tablettes
langues additionnelles. Egalement appelé Vocabulaire
Android et iPad.
Electrotechnique International (IEV) en ligne.

Recherche de publications IEC -
Glossaire IEC - std.iec.ch/glossary
webstore.iec.ch/advsearchform
67 000 entrées terminologiques électrotechniques, en anglais
La recherche avancée permet de trouver des publications IEC et en français, extraites des articles Termes et Définitions des
en utilisant différents critères (numéro de référence, texte, publications IEC parues depuis 2002. Plus certaines entrées
comité d’études,…). Elle donne aussi des informations sur les antérieures extraites des publications des CE 37, 77, 86 et
projets et les publications remplacées ou retirées. CISPR de l'IEC.

IEC Just Published - webstore.iec.ch/justpublished Service Clients - webstore.iec.ch/csc
Restez informé sur les nouvelles publications IEC. Just Si vous désirez nous donner des commentaires sur cette
Published détaille les nouvelles publications parues. publication ou si vous avez des questions contactez-nous:
Disponible en ligne et aussi une fois par mois par email. sales@iec.ch.

IEC 60268-3 ®
Edition 5.0 2018-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Sound system equipment –
Part 3: Amplifiers
Équipements pour systèmes électroacoustiques –

Partie 3: Amplificateurs
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.160.10 ISBN 978-2-8322-6243-6

– 2 – IEC 60268-3:2018  IEC 2018
CONTENTS
FOREWORD . 5
1 Scope . 7
2 Normative references . 7
3 Terms, definitions and rated values . 8
3.1 Terms and definitions . 8
3.2 Rated values . 9
4 Conditions . 9
4.1 Rated conditions and standard measuring conditions . 9
4.1.1 Overview . 9
4.1.2 Rated conditions . 10
4.1.3 Standard measuring conditions . 11
4.2 Other conditions. 11
5 Classes of operation . 11
6 Interchangeable parts . 11
7 Automatic controls . 11
8 Power supply . 12
9 Position of the volume controls . 12
10 Pre-conditioning for measurements . 12
11 Series of measurements . 12
12 Variable consumption apparatus . 12
13 Marking . 13
14 Operating environment . 13
15 Characteristics to be specified, and their methods of measurement . 13
15.1 Power supply characteristics . 13
15.1.1 Characteristics to be specified . 13
15.1.2 Method of measurement . 14
15.2 Tolerance of (long-term) power supply voltage variations . 14
15.2.1 Characteristic to be specified . 14
15.2.2 Methods of measurement . 15
15.3 Tolerance of power supply frequency variations . 15
15.3.1 Characteristics to be specified . 15
15.3.2 Methods of measurement . 16
15.4 Tolerance of power supply harmonics and ripple . 16
15.4.1 Characteristics to be specified . 16
15.4.2 Methods of measurement . 17
15.5 Input characteristics . 17
15.5.1 Rated source impedance, characteristic to be specified . 17
15.5.2 Input impedance . 17
15.5.3 Rated source e.m.f., characteristic to be specified . 19
15.5.4 Minimum source e.m.f. for rated distortion-limited output voltage . 19
15.6 Output characteristics . 19
15.6.1 Rated load impedance, characteristic to be specified . 19
15.6.2 Output source impedance . 20
15.6.3 Output voltage and power (distortion-limited) . 20
15.6.4 Maximum effective output power (distortion-limited at 10 %) . 22

15.6.5 Regulation . 23
15.6.6 Overload restoring time . 24
15.7 Limiting characteristics . 24
15.7.1 Overload source e.m.f. . 24
15.7.2 Short-term maximum output voltage and power . 24
15.7.3 Long-term maximum output voltage and power . 25
15.7.4 Temperature-limited output power . 26
15.8 Characteristics of protection circuits . 27
15.8.1 General . 27
15.8.2 Protection against potentially damaging combinations of output voltage
and current . 27
15.8.3 Characteristics of d.c. offset protection circuits . 28
15.9 Sustaining-time for rated (distortion-limited) output voltage or power . 29
15.9.1 General . 29
15.9.2 Characteristic to be specified . 31
15.9.3 Method of measurement . 31
15.10 Gain . 31
15.10.1 Voltage gain and e.m.f. gain . 31
15.10.2 Maximum e.m.f. gain . 31
15.10.3 Attenuation characteristic of the volume control . 32
15.10.4 Attenuation characteristic of balance controls for multi-channel
equipment. 32
15.11 Response . 33
15.11.1 Gain-frequency response . 33
15.11.2 Gain-limited effective frequency range . 33
15.11.3 Distortion-limited effective frequency range . 34
...