IEC 61606-2:2003 pdf – Audio and audiovisual equipment – Digital audio parts – Basic measurement methods of audio characteristics – Part 2: Consumer use

IEC 61606-2:2003 pdf – Audio and audiovisual equipment – Digital audio parts – Basic measurement methods of audio characteristics – Part 2: Consumer use.
1 Scope This part of IEC 61606 deals with the basic measurement methods of the audio charac- teristics of the digital audio part of audio and audiovisual equipment for consumer use. The common measuring conditions and methods are described in IEC 61606-1. Specific conditions and methods of measurement for consumer equipment are given in this standard. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 61606-1, Audio and audiovisual equipment – Digital audio parts – Basic measurement methods of audio characteristics – Part 1: General IEC 60268-2, Sound system equipment – Part 2: Explanation of general terms and calculation methods IEC 60958 (all parts), Digital audio interface IEC 61883-6, Consumer audio/video equipment – Digital interface – Part 6: Audio and music data transmission protocol IEC 61938, Audio, video and audiovisual systems – Interconnections and matching values – Preferred matching values of analogue signals 3 Terms, definitions, explanations and rated values 3.1 Definitions For the purposes of this part of IEC 61606, the terms and definitions given in IEC 61606-1 as well as the following apply. 3.1.1 analogue full-scale amplitude the nominal signal level of an EUT corresponding to the digital full-scale level NOTE In order to accommodate the EUT in an audio system, it is recommended that the analogue full scale amplitude has the value defined in IEC 61938. In the case of general purpose audio for consumer equipment, the amplitude is 2 V r.m.s. 3.1.2 normal measuring level analogue signal level equal to –20 dB of analogue full-scale amplitude
3.1.3 normal source impedance the value defined in IEC 61938, or in the case of general purpose audio for consumer equipment, 2,2 kΩ 3.1.4 normal load impedance the value defined in IEC 61938, or in the case of general purpose audio for consumer equipment, 22 kΩ 3.2 Explanation of terms See 3.2 of IEC 61606-1 3.3 Digital interface for measurement This standard can be applied to IEC 60958 or IEC 61883-6. Other interfaces having the same specification as in 3.1 of IEC 61606-1 may also be used. 3.4 Rated values For a full explanation of these terms, see IEC 60268-2. The following are rated conditions for digital audio equipment which should be specified by the manufacturer: • rated supply voltage; • rated supply frequency; • rated pre-emphasis and de-emphasis characteristics; • rated digital input word length; • rated sampling frequencies. 4 Measuring conditions The measuring conditions applied in this part are the same as those given in IEC 61606-1, together with those given below. 4.1 Environmental conditions As in IEC 61606-1. 4.2 Power supply As in IEC 61606-1. 4.3 Test signal frequencies As in IEC 61606-1. 4.4 Standard setting As in IEC 61606-1. 4.5 Preconditioning As in IEC 61606-1.
6.1.2.1.1 Input signal Frequency: 997 Hz. Signal level: from 0 V r.m.s. to in excess of the analogue full-scale level. 6.1.2.1.2 Procedure a) Equipment with digital output terminals 1) Set the EUT to the standard settings specified in 4.4. 2) Apply the input signal and increase the signal amplitude from 0 V r.m.s. If the level of the digital output terminal exceeds the normal measuring level (–20 dB FS ), adjust the level controller to maintain the output level to the normal measuring level. 3) Measure the input signal amplitude where further increase of the input signal level results in 1 % distortion in clipping of the output signal. 4) For EUT without a level control, measure the input signal level with 1 % distortion output signal. b) EUT without digital output terminals 1) Set the EUT to the standard settings specified in 4.4. 2) For EUT with an input signal level indicator, estimate the maximum non-clipping input signal level for the A/D converter. 3) Apply the input signal to the EUT and record the output signal to a recording medium for an input level range of –10 dB to +6 dB above the estimated non-clipping input signal level in 1 dB steps. 4) Measure the distortion of the output signal from the recorded medium using a player. 5) Measure the distortion a per cent exceeding 1 % and record the input signal level to the medium as A dB, and the distortion b %, which should be less than 1 %, with an input signal level (A – 1) dB. 6) Find the level L dB which gives distortion of 1 % to the EUT from the following equation: L dB = {A – (a – 1)/(a – b)} dB 7) In case both a and b exceed 1 %, or are less than 1 % , adjust the input signal level to the EUT so that an input signal is available where a exceeds 1 % and b is less than 1 %.