IEC 60268-3:2013

IEC 60268-3


®


Edition 4.0 2013-04



INTERNATIONAL



STANDARD



NORME
INTERNATIONALE


Sound system equipment –
Part 3: Amplifiers

Équipements pour systèmes électroacoustiques –
Partie 3: Amplificateurs


IEC 60268-3:2013

---------------------- Page: 1 ----------------------
THIS PUBLICATION IS COPYRIGHT PROTECTED


Copyright © 2013 IEC, Geneva, Switzerland


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 la CEI ou du Comité national de la CEI du pays du demandeur.

Si vous avez des questions sur le copyright de la CEI ou si vous désirez obtenir des droits supplémentaires sur cette

publication, utilisez les coordonnées ci-après ou contactez le Comité national de la CEI de votre pays de résidence.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé Fax: +41 22 919 03 00
CH-1211 Geneva 20 info@iec.ch
Switzerland www.iec.ch

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.

Useful links:

IEC publications search - www.iec.ch/searchpub Electropedia - www.electropedia.org
The advanced search enables you to find IEC publications The world's leading online dictionary of electronic and
by a variety of criteria (reference number, text, technical electrical terms containing more than 30 000 terms and
committee,…). definitions in English and French, with equivalent terms in
It also gives information on projects, replaced and additional languages. Also known as the International
withdrawn publications. Electrotechnical Vocabulary (IEV) on-line.

IEC Just Published - webstore.iec.ch/justpublished Customer Service Centre - webstore.iec.ch/csc
Stay up to date on all new IEC publications. Just Published If you wish to give us your feedback on this publication
details all new publications released. Available on-line and or need further assistance, please contact the
also once a month by email. Customer Service Centre: csc@iec.ch.


A propos de la CEI
La Commission Electrotechnique Internationale (CEI) 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 CEI
Le contenu technique des publications de la CEI est constamment revu. Veuillez vous assurer que vous possédez
l’édition la plus récente, un corrigendum ou amendement peut avoir été publié.


Liens utiles:

Recherche de publications CEI - www.iec.ch/searchpub Electropedia - www.electropedia.org
La recherche avancée vous permet de trouver des Le premier dictionnaire en ligne au monde de termes
publications CEI en utilisant différents critères (numéro de électroniques et électriques. Il contient plus de 30 000
référence, texte, comité d’études,…). termes et définitions en anglais et en français, ainsi que
Elle donne aussi des informations sur les projets et les les termes équivalents dans les langues additionnelles.
publications remplacées ou retirées. Egalement appelé Vocabulaire Electrotechnique
International (VEI) en ligne.
Just Published CEI - webstore.iec.ch/justpublished
Service Clients - webstore.iec.ch/csc
Restez informé sur les nouvelles publications de la CEI.
Just Published détaille les nouvelles publications parues. Si vous désirez nous donner des commentaires sur
Disponible en ligne et aussi une fois par mois par email. cette publication ou si vous avez des questions
contactez-nous: csc@iec.ch.

---------------------- Page: 2 ----------------------
IEC 60268-3



®



Edition 4.0 2013-04







INTERNATIONAL





STANDARD







NORME



INTERNATIONALE











Sound system equipment –

Part 3: Amplifiers




Équipements pour systèmes électroacoustiques –

Partie 3: Amplificateurs

















INTERNATIONAL

ELECTROTECHNICAL

COMMISSION


COMMISSION

ELECTROTECHNIQUE

PRICE CODE
INTERNATIONALE

CODE PRIX XB


ICS 33.160.10 ISBN 978-2-83220-735-2



Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

---------------------- Page: 3 ----------------------
– 2 – 60268-3  IEC:2013


CONTENTS


FOREWORD . 5

1 Scope . 7


2 Normative references . 7

3 Conditions . 8

3.1 Rated conditions and standard measuring conditions . 8

3.1.1 Overview . 8


3.1.2 Rated conditions . 8

3.1.3 Standard measuring conditions . 9
3.2 Other conditions . 9
4 Classes of operation . 9
5 Interchangeable parts . 10
6 Automatic controls . 10
7 Power supply . 10
8 Position of the volume controls . 10
9 Pre-conditioning for measurements . 11
10 Series of measurements . 11
11 Variable consumption apparatus . 11
12 Marking . 11
13 Operating environment . 12
14 Characteristics to be specified, and their methods of measurement . 12
14.1 Power supply characteristics . 12
14.1.1 Characteristics to be specified . 12
14.1.2 Method of measurement . 12
14.2 Tolerance of (long-term) power supply voltage variations . 13
14.2.1 Characteristic to be specified . 13
14.2.2 Methods of measurement . 13
14.3 Tolerance of power supply frequency variations . 14
14.3.1 Characteristics to be specified . 14
14.3.2 Methods of measurement . 14
14.4 Tolerance of power supply harmonics and ripple . 15
14.4.1 Characteristics to be specified . 15

14.4.2 Methods of measurement . 15
14.5 Input characteristics . 15
14.5.1 Rated source impedance, characteristic to be specified . 15
14.5.2 Input impedance . 15
14.5.3 Rated source e.m.f., characteristic to be specified . 17
14.5.4 Minimum source e.m.f. for rated distortion-limited output voltage . 17
14.6 Output characteristics . 18
14.6.1 Rated load impedance, characteristic to be specified . 18
14.6.2 Output source impedance . 18
14.6.3 Output voltage and power (distortion-limited) . 19
14.6.4 Regulation . 20
14.6.5 Overload restoring time . 20
14.7 Limiting characteristics . 21
14.7.1 Overload source e.m.f. . 21

---------------------- Page: 4 ----------------------
60268-3  IEC:2013 – 3 –


14.7.2 Short-term maximum output voltage and power . 21

14.7.3 Long-term maximum output voltage and power . 22

14.7.4 Temperature-limited output power . 23

14.8 Characteristics of protection circuits . 24

14.8.1 General . 24

14.8.2 Protection against potentially damaging combinations of output

voltage and current . 24

14.8.3 Characteristics of d.c. offset protection circuits . 25

14.9 Sustaining-time for rated (distortion-limited) output voltage or power . 26

14.9.1 General . 26

14.9.2 Characteristic to be specified . 27
14.9.3 Method of measurement . 28
14.10 Gain . 28
14.10.1  Voltage gain and e.m.f. gain . 28
14.10.2 Maximum e.m.f. gain . 28
14.10.3 Attenuation characteristic of the volume control . 28
14.10.4 Attenuation characteristic of balance controls for multi-channel
equipment . 29
14.11  Response . 30
14.11.1 Gain-frequency response . 30
14.11.2 Gain-limited effective frequency range . 30
14.11.3 Distortion-limited effective frequency range . 31
14.11.4 Phase-frequency response . 31
14.12 Amplitude non-linearity . 31
14.12.1 General . 31
14.12.2 Rated total harmonic distortion, characteristic to be specified . 31
14.12.3  Total harmonic distortion under standard measuring conditions . 32
14.12.4 Total harmonic distortion as a function of amplitude and frequency . 32
14.12.5  Harmonic distortion of the nth order under standard measuring
conditions . 33
14.12.6  Harmonic distortion of the nth order as a function of amplitude and
frequency . 34
14.12.7  Modulation distortion of the nth order (where n = 2 or n = 3) . 34
14.12.8 Difference-frequency distortion of the nth order (where n = 2 or n =
3) . 36
14.12.9 Dynamic intermodulation distortion (DIM) . 37

14.12.10 Total difference frequency distortion . 39
14.12.11 Weighted total harmonic distortion . 40
14.13 Noise . 41
14.13.1  Characteristic to be specified . 41
14.13.2  Method of measurement. 41
14.14 Hum . 42
14.14.1 General . 42
14.14.2  Characteristics to be specified . 42
14.14.3 Method of measurement. 42
14.15 Balanced inputs and outputs . 43
14.15.1 Balance of the input . 43
14.15.2  Overload (distortion-limited) peak-to-peak common-mode input
voltage . 44
14.15.3  Balance of the output . 44

---------------------- Page: 5 ----------------------
– 4 – 60268-3  IEC:2013


14.16 Cross-talk and separation in multi-channel amplifiers . 46

14.16.1 Characteristics to be specified . 46

14.16.2 Method of measurement. 46

14.17 Gain and phase differences between channels in multi-channel amplifiers . 47

14.17.1  Gain difference . 47

14.17.2 Phase difference . 48

14.18 Dimensions and mass, characteristics to be specified . 48

Annex A (informative) Balanced interfaces . 56

Annex B (informative) Specification of a multi-channel amplifier. 57

Bibliography . 59

Figure 1 – Example block diagram for multi-channel amplifier . 49
Figure 2 – Arrangements for the Class D amplifier . 50
Figure 3 – Arrangements for measuring input impedance . 51
Figure 4 – Oscillogram when measuring overload restoring time . 52
Figure 5 – Protection against potentially damaging combinations of output voltage and
current . 53
Figure 6 – Arrangement for combining two input signals . 54
Figure 7 – Frequency spectrum below 30 kHz of the signal for measuring dynamic
intermodulation distortion . 54
Figure 8 – Arrangement for measuring the balance of a balanced input . 55
Figure 9 – Arrangement for measuring the internal impedance balance of a balanced
output . 55
Figure 10 – Arrangement for measuring the voltage symmetry of a balanced output . 55
Figure B.1 – Block diagram for a 5.1 channel surround amplifier . 57
Figure B.2 – Block diagram for a 5 channel surround amplifier . 58

Table 1 – Different rated total harmonic distortion and rated distortion-limited output
power specifications for the same amplifier . 27
Table 2 – Distortion components due to dynamic intermodulation distortion falling in
the frequency range up to 20 kHz . 38

---------------------- Page: 6 ----------------------
60268-3  IEC:2013 – 5 –


INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________



SOUND SYSTEM EQUIPMENT –



Part 3: Amplifiers





FOREWORD


1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60268-3 has been prepared by IEC technical committee 100:

Audio, video and multimedia systems and equipment.
This fourth edition cancels and replaces the third edition published in 2000. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
– rated condition of multi-channel amplifier is expanded;
– arrangement for the D-class amplifier is added;
– method of measurement for output power (distortion-limited) is expanded;
– Annex B is newly added.

---------------------- Page: 7 ----------------------
– 6 – 60268-3  IEC:2013


The text of this standard is based on the following documents:

FDIS Report on voting


100/2010A/CDV 100/2066/RVC



Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table.


This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.


A list of all parts in the IEC 60268 series, published under the general title Sound system
equipment, can be found on the IEC website.
This part of IEC 60268 shall be used in conjunction with IEC 60268-1:1985 and
IEC 60268-2:1987.

---------------------- Page: 8 ----------------------
60268-3  IEC:2013 – 7 –


SOUND SYSTEM EQUIPMENT –



Part 3: Amplifiers







1 Scope


This part of IEC 60268 applies to analogue amplifiers, and the analogue parts of

analogue/digital amplifiers, which form part of a sound system for professional or household
applications. It specifies the characteristics which should be included in specifications of
amplifiers and the corresponding methods of measurement.
1
NOTE The methods of measurement for digital amplifiers and similar equipment are given in IEC 61606 [4] .
In general, the specified methods of measurement are those which are seen to be most
directly related to the characteristics. This does not exclude the use of other methods which
give equivalent results.
In general, the methods are based on the simplest measuring equipment which can provide
useful results. This does not exclude the use of more complex equipment which can give
higher accuracy and/or allow automatic measurement and recording of results.
Rated conditions and standard measuring conditions are specified in order to allow
measurements to be reliably repeated.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60065:2001, Audio, video and similar electronic apparatus – Safety requirements
Amendment 1:2005
Amendment 2:2010
IEC 60268-1:1985, Sound system equipment – Part 1: General
Amendment 1:1988

Amendment 2:1988
IEC 60268-2:1987, Sound system equipment – Part 2: Explanation of general terms and
calculation methods
Amendment 1:1991
IEC 60417, Graphical symbols for use on equipment. Available from: http://www.graphical-
symbols.info/equipment
IEC 61000-4-13:2002, Electromagnetic compatibility (EMC) – Part 4-13: Testing and
measurement techniques – Harmonics and interharmonics including mains signalling at a.c.
power port, low frequency immunity tests
Amendment 1:2009
––––––––––––
1
 Numbers in square brackets refer to the Bibliography.

---------------------- Page: 9 ----------------------
– 8 – 60268-3  IEC:2013


IEC 61000-4-17:1999, Electromagnetic Compatibility (EMC) – Part 4-17: Testing and

measurement techniques – Ripple on d.c. input power port immunity test

Amendment 1:2001

Amendment 2:2008


IEC 61000-4-29:2000, Electromagnetic Compatibility (EMC) – Part 4-29: Testing and

measurement techniques – Voltage dips, short interruptions and voltage variations on d.c.

input power ports immunity tests


IEC 61938:1996, Audio, video and audiovisual systems – Interconnections and matching

values – Preferred matching values of analogue signals

3 Conditions
3.1 Rated conditions and standard measuring conditions
3.1.1 Overview
For convenience in specifying how amplifiers shall be set up for measurement, sets of
conditions are specified in this standard, under the titles of rated conditions and standard
measuring conditions.
A full explanation of the term "rated" is given in IEC 60268-2.
The rated conditions for amplifiers are:
– rated power supply voltage;
– rated source impedance;
– rated source e.m.f.;
– rated load impedance;
– rated total harmonic distortion, or rated (distortion-limited) output voltage or power;
– rated mechanical and climatic conditions.
NOTE 1 Total harmonic distortion and (distortion-limited) output voltage or power are interdependent. Both cannot
be taken as rated conditions simultaneously because normally a given sample amplifier produces less than rated
total harmonic distortion at rated output voltage or power.
NOTE 2 If the power supply frequency is critical, it is also a rated condition.
To obtain the correct conditions for measurements, the values for the above-mentioned rated
conditions shall be taken from the manufacturer's specification. These values themselves are

not subject to measurement but they constitute the basis for measuring the other characteristics.
Methods of measurement for these other characteristics are given in this standard and the
manufacturer is either required or permitted to state 'rated values' for these characteristics in
the specification of the equipment. These include
– rated voltage gain;
– rated distortion limited output voltage or power (when not adopted as a rated condition);
– rated signal-to-noise ratio;
– rated equivalent noise source e.m.f.
3.1.2 Rated conditions
An amplifier, considered as a four-terminal network with regard to a specified pair of input
terminals and a specified pair of output terminals, shall be understood to be working under
rated conditions when the following conditions are fulfilled:

---------------------- Page: 10 ----------------------
60268-3  IEC:2013 – 9 –


a) the amplifier is connected to its rated power supply;

b) the source e.m.f. is connected in series with the rated source impedance to the input

terminals;

NOTE 1 Multi-channel amplifiers can be specified with any number of channels driven, or all channels. See

Annex B. The input signal can be applied simultaneously to all inputs of similar channels.

c) the output terminals are terminated with the rated load impedance;

NOTE 2 For the measurement of Class D a
...