Audio Engineering Society Standards Committee

Comments on digitally interfaced microphone standard

[Last printing 3 June 2001] Comments to date on Draft AES42-xxxx, DRAFT AES standard for acoustics -- Digital interface for microphones published 2000-09-07 for comment.

Schmidt 2000-09-19


Fro

To:     standards@aes.org
Subj: Re: Call For Comment Draft AES42

This is in reply to the Call for Comment dated September 6, 2000 on Draft AES 42, AES Standards for Acoustics - Digital Interface for Microphones.

I am concerned that the issue of the standard 3 pin XLR still needs work. As many of those who have worked on this standard are aware, I and others were originally concerned about the use of that connector mostly from a point of user confusion; 'Why won't my microphone work even though it's plugged in a mating connector?'. The XLD connector was developed as an alternative connector to alleviate those concerns.

Over the last few months, the potential for damage to (mostly analog) equipment(particularly equipment outputs terminated in male XLR connectors), if connected inadvertently to digital microphone receiver inputs, has received much discussion. It is my opinion that the current wording of AES42 inadequately addresses this issue.

There was a feeling in the committee that it was important to get the draft standard released promptly in the Call for Comment. I agree with that feeling, but I feel that the interconnectivity issue and the potential for damage to equipment needs to be fully addressed.

We have developed the solution to the interconnectivity, and therefore the potential damage problem: the XLD connector with its coding scheme. But the document as worded makes the XLD appear to be a poor sister, to be given only secondary consideration. I feel this should be changed before the standard is issued. If we are not ready to take the big step and make the XLD the only specified, or even the recommended, connector, we should at least put it on an equal footing with the XLR, and to recommend that it, and its coding, be used where either equipment damage or user confusion may be an issue.

AES42, as written does not even require manufacturers of compliant microphones or receivers to make them available with XLD connectors as an option. When the SC-04-04-E task group was discussing the connector issue, I raised this issue, I think on one of our conference calls, and was assured by the microphone manufacturers that they would, in fact, offer such microphones. This requirement seems to have been left out of the specification.

Even the Foreword, as written, downplays the use of the XLD. The wording of the 5th paragraph does reflect the position of the standard as drafted (although I am proposing we revise the draft) , but the statement in paragraph 6 that the XLD is not required and the working group has taken no position on its efficacy is, to me, unnecessarily negative. If the connector will meet the requirements of the standard, it should have the backing of the working group. If it doesn't meet the requirements, it shouldn't be in the document.

Perhaps SC-05-02, the sub-committee on single program connectors should be asked to determine the efficacy of the XLD connector on an expedited basis.

I will not try to put words in the mouths of the writers of the foreword, as it is not a part of the standard, but I feel it should be reworded to address these concerns.

Specific paragraphs I feel should be changed are 4.2:

Proposed rewording:

"The XLD connector described in Annex E or the 3-contact XLR connector described in AES14 shall be used."

4.2.1: Proposed Rewording:

"Users who are concerned about preventing intermating with equipment using XLR connectors, either to prevent equipment damage or to avoid user confusion, should use the fully coded XLD connector."

NEW Paragraph:

"Manufacturers of compliant microphones and receivers shall use XLD connectors as the interface. They may also offer them with an XLR connector option. XLD's as shipped shall be fully coded, as described in Annex E."

Another issue concerns the power supply short-circuit current:

There is not now an upper limit on the current provided by the AES3-MIC receiver's power supply under fault conditions. The second paragraph of 5.1 simply says "The voltage source shall be protected against possible short circuits..." We need to put an upper limit on the available current this "protection" allows under fault conditions. I am aware there are discussions still underway about various 'safe startup' schemes to prevent powering the microphone unless a handshake takes place, but this is a different issue: what is the safe upper limit on the current provided from the receiver. Some equipment and cable uses quite small gauge wire, and it is quite possible that even one Ampere of sustained short current could smoke it. This is only four times the upper limit of the microphone's normal operating current.

As a matter of style and to avoid confusion, I feel paragraph numbers should be added to many of the sub paragraphs in the standard. For instance there should be a 5.1.1 and a 5.1.2. This should be done consistently throughout the document.

John Schmidt


Brown 2000-09-22


From:   SMTP%"jimbrown@enteract.com" 22-SEP-2000 17:31:41.42
To: "standards@aes.org"
Subj: Comments on AES42 Draft

Comments on Draft AES42-xxxx.

This is in reply to Call for Comments dated 6 Sept 2000 on Draft AES 42.

My primary concern is that the connector scheme specified does not satisfactorily address use of digital microphones in the wide variety of venues where they will be used. If this standard is to be successful, digital microphones must work reliably in theaters, performing arts centers, broadcast facilities, studio complexes, and academic performance complexes. They must be function reliably with both new and existing facilities. The conditions in general existence are:

1. Microphones in these facilities are routed to input equipment via tie lines, typically 100 m - 200 m in length. These tie lines utilize cable types designed for analog audio and are almost universally foil/drain shielded cables which do not have controlled impedance or transmission line characteristics. These tie lines utilize XLR connectors.

2. These tie lines are often routed via patch panels. It is common for patch cables to be of different construction and impedance from the tie lines themselves. It is also common for them to be patched on quarter inch jacks, and to be routed through "Christmas tree" wiring blocks.

3. It is common for tie lines to be split to feed more than one input (i.e., two or three mix consoles bridging each mic). Splitting transformers are used in some installations, while in others mixer inputs are directly wired in parallel.

4. Conditions 1, 2, and 3 are all clearly destructive of the digital signal. Tests at ABC New York have found that an unspliced 500 ft length of foil/drain shielded cable of the type most commonly used for permanent installations (Belden 8451) will not pass digital audio at all. Some types designed for analog audio will pass digital audio under some conditions.

5. While some cables not designed for digital audio do provide acceptable transport of digital signals, others do not. The determination must be made on site as to the acceptability of each and every tie line for digital audio transport. If digital audio is to be reliably fed around facilities, it MUST be on cable infrastructure which is either designed for digital audio or whose performance has been verified for digital audio.

6. Operating personnel are often low paid, poorly trained, and transient from one facility to another. Seldom are they aware of the technical limitations of the infrastructure, especially its wiring. Often they may have little technical competence. Even the best trained and most skilled will often move from one facility to another, and will often be working in a facility with which they are not familiar. While none of us endorse these realities, they are not likely to change in the foreseeable future.

7. It is not acceptable to simply assume that digital audio signals will all be transported on some form of analog or digital multiplex system. In many live applications, the latency of such systems, combined with latency of other system elements, precludes the use of multiplexed transport.

8. The cost of wiring and routing infrastructure is generally at least an order of magnitude greater than the cost of the microphones that will be used with that infrastructure. The cost of upgrading that infrastructure is primarily labor, and is essentially the same as its initial cost, multiplied by any associated inflation. It must be assumed that existing wiring infrastructure will remain in place in most facilities for at least 10-20 years. What is safe to assume is that tie lines for digital microphones will be added to those facilities.

The inescapable conclusion which must be drawn from these real world conditions is that digital audio equipment, digital audio signals, and digital audio infrastructure MUST be clearly identified, and MUST utilize a connector which limits the connection of digital signals to digital transmission circuits.

I believe that the physical connector logic developed by Neutrik as described in the Annex is a very good one, provided that: the use of the fully coded XLD connector shall be made exclusive and mandatory for all digital microphones, and; that digital microphones shall not be manufactured or used with XLR connectors, and; the XLD connector is not readily field modifiable, and; the use of half coded connectors shall be limited to those elements of the infrastructure which are capable of passing the digital audio signal reliably and without degradation.

This conclusion requires revisions of: The Foreword must be revised to state that fully coded XLD connectors shall be used for all digital microphones, their associated receivers, and wiring.

4.2 must be revised as follows:

"Manufacturers of compliant microphones and receivers shall use only fully coded XLD connectors as the interface, except that half coded connectors shall be utilized only on receivers capable of receiving and processing both analog and digital signals."

4.2.1 must be deleted.

4.2.2 should be renumbered.

4.2.3 should be renumbered.

A new paragraph should be added as follows:

"Compliant interconnection cables for portable use shall utilize only fully coded XLD connectors." [Explanatory Note: While cables designed for digital use may carry analog signals without degradation, it should not be possible to connect a cable carrying digital audio to a cable or receiver which is not capable of carrying receiving digital audio.]

Jim Brown


Olson 2000-09-22


From:   SMTP%"OlsonSound@hotmail.com" 22-SEP-2000 20:04:30.14
To:
Subj: Call for Comment Draft AES42

To: Standards@aes.org

From: Bruce C. Olson

Date: 9/22/2000

Re: Call for Comment Draft AES42

This is in reply to the Call for Comment dated Sept. 6, 2000 on Draft AES 42, AES Standards for Acoustics - Digital Interface for Microphones.

The allowance of the use of 3-contact XLR connectors in paragraph 4.2 is not acceptable due to the likely possibility of damage to analog equipment by inadvertent connection to digital microphone receiver equipment, first of all. In addition, even if damage does not occur, many real facilities will have problems of microphones not working when typical users plug in analog microphones to digital microphone circuits that have identical connectors.

The significance of labeling and/or color-coding only being used to differentiate digital circuits from analog circuits is not sufficient for the typical users of these systems.

The solution to these problems is to use a fully-coded connector, of course, and should be the recommended practice. Allowing the use of a field-modifiable XLD that allows it to be converted to a standard 3-contact XLR only delays the outbreak of the problems noted above. Therefore, under 4.2.1, XLD connectors for use with equipment compliant with this standard shall be fully-coded and not user modifiable.

Bruce C. Olson


Rayburn 2000-09-23


From:   SMTP%"audio@technologist.com" 23-SEP-2000 03:33:37.68
To: standards@aes.org
Subj: Draft AES42-xxxx CFC

I agree with the thrust of the comments by John Schmidt submitted 2000-09-19, and Jim Brown submitted 2000-09-22.

I would like to suggest that the NEW Paragraph proposed by John Schmidt have the second (of three) sentence deleted. The modified NEW Paragraph would read:

Manufacturers of compliant microphones and receivers shall use XLD connectors as the interface. XLD's as shipped shall be fully coded, as described in Annex E.

There is no need to allow the use of standard XLR type connectors since the user can remove the keying if they so desire. Only providing one type of connector will make for manufacturing efficiencies.

While I agree with Jim Brown that XLD's without removable keying would be desirable, keeping the keying removable will be of benefit to those who have large inventories of exising cables and tie lines they feel are satisfactory for AES3 digital audio, and are willing to take the risks involved with removing the keying.

Of course nothing should stop those manufacturers who so wish to equip their AES42 equipments with XLD connectors without removable keying. Neutrik has indicated that this would be a less expensive connector than the removable keying version.

Requiring the use of the XLD connector will also solve the issue of "safe DPP". At the SC-04-04-D meeting today, all the proposed schemes for safe DPP involved modification of both the microphone and the receiver. Unless a suitable single ended safe DPP scheme is developed before the end of the AES42 CFC period, I am of the opinion that this alone should be reason enough to mandate the use of the XLD in AES42.

Ray A. Rayburn chair SC-05-02 Audio@Technologist.com


Dunn 2000-09-25


From:   SMTP%"JDunn@iee.org" 25-SEP-2000 17:36:19.99
To: AES Standards Secretariat
Subj: Call For Comment on Draft AES42-xxxx

The proposal in AES42 to allow a new type of connector, the XLD, is an attempt at compromise between maintaining compatibility with the standard AES3 interface (so that while the cabling and connections can be shared) and providing protection for existing analogue equipment that may be damaged by the application of digital phantom power.

(There is also a desire to avoid problems that the attempted connection of analogue and digital interfaces can produce when cables appear the same. However, this issue relates not just to AES42 but all AES3 connections and equipment, so it is not resolvable in this document)

This attempt at compromise has several disadvantages. Some have been raised by objectors already in that the optional requirement for the XLD and the user-optional coding key permits accidental connection with analogue interfaced equipment that can still cause damage.

In addition the use of the XLD would raise an incompatibility with AES3 that - to some extent - would defeat the purpose of using that format for this new interface. It would mean that AES3 signals could not be connected to any AES42 inputs that have coded XLD connectors. This would either mean that the XLDs would be left un-coded (so defeating the protection) or that manufacturers of equipment intended for connection to either AES42 or AES3 would need to have separate connectors for each.

Therefore I propose that AES42 is changed to remove reference to the XLD connector and to require that the application of the common mode power is controlled in such a way as to limit the risk of damage to analogue outputs. As analogue outputs are not constrained by standards to have any protection this would be impossible to guarantee. However the risk of damage can be set to be lower than the current risk from analogue phantom power circuits.

This "Safe Digital Phantom Power" should be defined such that, until a digital audio signal has been recognised, the current and voltage are both limited to less than that of a typical analogue phantom power system. As well as imposing DC constraints this restriction will require that the power source not be capable of the short-term high current that the typical analogue microphone preamplifier is capable of through its DC blocking capacitor.

The AES42 transmitter (microphone) sends the digital audio signal using the limited power initially available. This can be either through using a charge storage system and transmitting only after enough charge is available or by using a low power circuit while the remaining part of the device remains disabled. The AES42 receiver raises the current limit to the 250mA within a defined period of recognising the source as digital.

This will obviously need to be prototyped before a second issue of the call for comment can be made.

Julian Dunn


Henkel 2000-09-30


From:   SMTP%"hartmut_henkel@gmx.de" 30-SEP-2000 15:53:22.13
To: AESSC Secretariat
Subj: DRAFT AES42-xxxx Comments

Dear Madams, dear Sirs,

please have my comments to the

``Call for Comment on DRAFT AES standard for acoustics --- Digital interface for microphones'',

(Secretariat 2000/09/04 12:52 CFC DRAFT AES42-xxxx):

* p. 7, 3.2.2: Instead of `least-significant' write `least significant', to be consistent with `most significant'.

* p. 7, 4.2.2: Instead of `annex E' write `Annex E', for consistency.

* p. 10, 1st NOTE: Instead of `annex D' write `Annex D'.

* p. 10, 2nd NOTE: Instead of `Instruction' write `instruction'.

* p. 10, A.1.1: Instead of `annex B' write `Annex B'.

* p. 10, Figure A.1: I would like to suggest to mirror the picture, so that the `Mixing console' will be on the right side, and the `Digital microphone' on the left side. Then the MSB in the transmitted word is left, and the LSB is right, which is consistent with other tables, and helps understanding.

* p. 11, below Table A.1: Instead of `table A.2' write `Table A.2'.

* p. 11, below Table A.2: Instead of `tables' write `Tables'.

* p. 13, Figure A.2: Please mirror this also, see remark to Figure A.1.

* p. 13, Table A.11: Instead of `Dither-noise shaping' write `Dither and noise shaping', for consistency.

* p. 15, Table A.20: The table of settings is misleading due to wrong rounding of values. E.g. left and right channel do not sum up to one, and the value 0,984375 (63/64) in my opinion cannot be brought into a linear relationship.

There are two possible corrections. First, see the following table, which straightens out the plain error in the original Table A.20, and by clean sorting and added intermediate steps gives better understanding of the interrelationship. The correspondence between bit value and setting is now linear.

---Corresponding setting---


Bit value   Left channel   Right channel   Balance
-----------------------------------------------------------------
0111111 0,9921875 0,0078125 Left (A) channel only
.. ... ...
0000001 0,5078125 0,4921875 Smallest step to left
0000000 0,5 0,5 Center, default
1111111 0,4921875 0,5078125 Smallest step to right
.. ... ...
1000000 0,0 1,0 Right (B) channel only

The left channel is calculated there by (/64+1)/2.

What is not nice there (and in the original Table A.20) is the unsymmetry in treatment of the left and right channels, and that there is no clean Left channel only, with Right channel off. Let me therefore suggest that the Right (B) channel saturates already one step before the extreme Bit value, and that there is a clean Left (A) channel only. This gives the second table:

---Corresponding setting---


Bit value   Left channel   Right channel   Balance
-----------------------------------------------------------------
0111111 1,0 0,0 Left (A) channel only
.. ... ...
0000001 0,5079365 0,4920635 Smallest step to left
0000000 0,5 0,5 Center, default
1111111 0,4920635 0,5079365 Smallest step to right
.. ... ...
1000001 0,0 1,0 Right (B) channel only
1000000 0,0 1,0 Same as for 1000001

The left channel is calculated there by (/63+1)/2.

* p. 15, NOTE: Instead of of putting the NOTE below Table A.21, put the NOTE below Table A.20.

* p. 16, Figure A.3: For clarification add three directional arrows on top of the bus lines towards `Control data'.

* p. 16, Figure A.3: For clarification add three directional arrows at the three `enable lines' towards the `Direct command shift register's.

* p. 16, Figure A.3: Instead of `enable' write `latch enable', to make clear, that not the shift register is enabled, but only its output latch (the shift register itself is operated continuously).

* p. 16, 2nd paragraph: Instead of of `bytes 4 to 35' write `bytes 4 to 34'. Further remarks to section A.4 see below.

* p. 19, Structure of the remote control pulses:

Instead of `7 - 64/8f_s' write `7 * 64 / (8 f_s)'.
Please do not omit the braces () above shown.
Instead of `1 - 64/8f_s' write `1 * 64 / (8 f_s)'.
Instead of `7 - 64/8f_s' write `7 * 64 / (8 f_s)'.
Instead of `1 - 64/8f_s' write `1 * 64 / (8 f_s)'.
Instead of `16 - 64/8f_s' write `16 * 64 / (8 f_s)'.
Instead of `for example, 21,28 ms' write `for example, 21,33 ms'.
Instead of `8 - 64/8f_s' write `8 * 64 / (8 f_s)'.
Instead of `4 - 64/8f_s' write `4 * 64 / (8 f_s)'.

* p. 19, Figure B.1: Two times: Instead of of `10,64 ms' write `10,67 ms'. In the figure change all decimal points `.' into decimal commata `,'. Instead of `7x64/8f_s' write `7 * 64 / (8 f_s)'; be consistent with the text.

* p. 21, C.3: There is written, that the `Averaging time constant (C3, R3) should not exceed 10 ms. But the hardware example on page 22 gives for the same time constant the value C3 * R3 = 4,7 s, which is a contradiction to the recommendation done on the previous page. I believe that on page 21 instead of `should not exceed' it should be `should not be lower than'.

* p. 26, Table D.8: Instead of `Dither-noise shaping' write `Dither and noise shaping'.

-----

Further, since the section A.4 reads rather nebulous and in part incorrect (e. g., not all four shift registers are in parallel), I have tried to make a wording for this section, which should describe things clearer:

* p. 16, A.4 Hardware example, simple instruction mode

The remote control instruction pulses, which are common-mode signals on the MIC wires, are decoupled from the center tap of the AES3 transformer within the MIC. A capacitor between the center tap and MIC ground reduces the effects of radio frequency (RF) interference in the cable. An optional decoupling circuit in front of the MIC voltage regulator allows to use higher instruction data rates even though the regulator needs a large capacitor for input filtering. Without the decoupling circuit, this large capacitor together with the cable resistance would constitute a low-lass (LP) filter and limit the maximum instruction data rate.

A data recovery circuit splits the incoming remote control instruction pulses into data, clock, and latch enable pulses. The data are shifted through three 8-bit `Direct command' shift registers in parallel, and then into the 8-bit `Address' shift register. All four shift registers are equipped with output latches. The address byte, which is received first, will be transfered into the output latch of the address shift register, setting one direct-command enable bit. This bit latches the control data byte from the corresponding direct command shift register into its output latch. The control data (command bytes 1 to 3) are used to directly control hardware. If a very simple microphone just controls the basic features (for example, features in command byte 1) it is possible to implement only direct command shift register 1 and address shift register. If a micro-controller is used for implementing extended instruction mode, the address shift register will be read out by the controller according to the 5-bit address in the address byte (five MSBs) to use command bytes 4 to 34. The structure may also be implemented using a Digital Signal Processor (DSP), field-programmable logic (FPGA), or ASIC.

I would be glad to have your comments.

Best Regards

Hartmut Henkel

Dr.-Ing. Hartmut Henkel
In den Auwiesen 6
D-68723 Oftersheim
Germany
E-Mail: hartmut_henkel@gmx.de


Reply to Henkel 2000-12-24


From:   SMTP%"david@josephson.com" 24-DEC-2000 17:51:17.38
To: standards@aes.org
Subj: Reply to Henkel

Dear Mr Henkel,

This is in response to your comments on the proposed digitally interfaced microphone standard, AES42-XXXX. I'm sure I speak for the working group and the AES Standards Committee in thanking you for the energy and efforts that you have put in toward working out the best possible standard to guide manufacturers' and audio engineers' efforts in the years to come. I am particularly happy to have had your careful analysis of the technical wording of the proposed standard.

As you know the procedures of the AESSC require a formal consideration of all comments, and a response to each, from the chair of the working group. The Steering Committee will consider your comments, my response as chair of the WG, and any resolution we can conclude, in deciding how to progress the proposed standard. The AESSC's options are to approve the standard as is, to approve it as a trial use standard, or to send it back to the working group for revision or withdrawal. We cannot substantially revise the draft without reissuing the proposed standard beginning another three-month comment period. Substantive objections to the proposed wording, if they are not resolved by discussion or editorial change, suggest to the Steering Committee that a consensus of affected parties does not exist and that a standard should not be approved. If the objecting commenters can reach some resolution which allows them to agree with an editorially adjusted standard, the Steering Committee is more inclined to approve the proposed work.

I believe that all of the changes you have suggested are of an editorial nature. During the telephone conference of the SC-04-04 and SC-04-04-D working groups on 2000-12-20, there was general agreement that your points were well taken and should be incorporated. I believe that a simple solution has been devised for the issue of Table A20, showing simply the full left, center and full right codes. Each manufacturer will work out his own intermediate values according to his design.

Your comments are being forwarded to the AESSC Secretariat with my recommendation that the suggested editorial changes be considered as written consistent with AESSC and IEC style. If you have any further comments, agreement or disagreement, please reply before 2001-01-10, with a copy to the AESSC Secretariat , whether or not this reply is acceptable to you. Of course, the AESSC procedures also point out that you may also ask us to consider your comments again for the next revision of the document, and that you may appeal the final decision to the Standards Secretariat as described in much detail in the AESSC Procedures.

Thanks and best regards, David Josephson Chair, SC-04-04


Paul 2000-11-14


From:   SMTP%"jonpaul@linkline.com" 14-NOV-2000 16:17:30.05
To: standards@aes.org
CC: Tony.Agnello@ariel.com
Subj: Call for comment DRAFT AES42-xxxx: Patents, Phantom Power Transformers

Gentlemen:

In response to the call for comment, please consider the following items.

on Page 5: par. 0.1 Patents:

a/ The US Patent 5,051,799, (applied for in 1989) long precedes the SGS-Thompson application of 1995. Since the SGS EPO application is not yet allowed, can US 5,051,799 be mentioned before the SGS application?

b/: The listed contact information for US 5,051,799 is wrong, please correct the information to:


Jon D. Paul, V.P.=09
Scientific Conversion, Inc.
42 Truman Drive Novato, CA 94947 USA
Web inquiry@scientificonversion.com
telephone +001-415-892-2323 fax: +001-415-892-2321

c/ SGS: What is the status of SGS vis a vis the AES patent agreement. Have they been contacted? Does SGS agree or refuse? (note the SGS company name has changed to STMicroelectronics).

2/ Block diagram and schematic of the interfaces on pages 16, 17,18, 22: In Figs A.3, A.4, A.5, C.1, The transformer designation and specification is vague.

The designation "AES3 transformer" in the upper left hand block of fig. A.4 misleading since AES3 does not specify a center tapped transformer! Adding the center tap requires additional specifications, e.g. maximum DC current, balance, etc which are not in AES3.

Here is a typical specification we provide for such a transformer, our SC983-05. The * items are specially applicable to the digital microphone application.

SPECIFICATIONS: TRANSFORMER SC983-05


        Ratio   1:1 center tap
Ind, primary/sec 1000 uH typ
Inductance, leakage 500 nH typ
Pri-sec capacitance 5 PF typ
E-T product 35 V-uS typ
* CT D.C. current 500 mA typ
* CT CMRR @ 100 kHz >70 dB
Resistance pri/sec 0.700 Ohm
* Bandw. 110 ohm 10 KHz-72 MHz
* Voltage isolation P-S 500 VDC
Risetime in 110 Ohm Z 5 nS typ
Size 6.3mm x 9.5mm x 8.2mm max

3/ Page 18, partslist, TR1: "transformer according to AES3, 6.1" same comment as above.

A typical commercially available part that can be placed in the component list is our SC983-05. Can TR1 on p. 18 fig. A.5 parts list be changed to show this example?

4/ The diagrams do not show any details for filtering of the power feed to the transformer center tap. We have found the insertion of a small inductor in series with the transformer center tap connection to be useful in reducing high frequency power supply current noise or ripple. A typical part is our SC955-02 Micro-Toroid Filter Inductor. Here is a specification for that part.

SPECIFICATIONS TOROID SC955-02


        Ind. 1 kHz - 300 kHz    68 uH +/- 10%
Ind. 1kHz @ 0.5A DC 68uH - 10%
Resistance 0.500 Ohm Max
Maximum Current 0.5 A
Self res freq 9 MHz
Energy storage 0.5A 8.5 uJ
Size 3mm H x 7mm dia

Thank you for your kind consideration of these items.

With Kind Regards,

Jon Paul


Skirrow 2000-11-25


From:   SMTP%"lindos@zetnet.co.uk" 25-NOV-2000 13:23:17.19
To: standards@aes.org
Subj: call for comments - draft AES42

Hello

This is in reply to the Call for Comment dated 6 Sept 2000 on Draft AES42

I agree with earlier comments aimed at eliminating the possibility of damage to analogue equipment, but would urge most strongly that this problem is best solved by the specification of a new, smaller Universal Digital Connector, and the renaming of this standard as "AES Standard - Universal Digital Interface."

Most of the work on this draft standard so far has understandably been aimed at what might be called 'high-end' microphone applications, with particular attention to the problems of driving very long lines in existing studio infrastructures. It seems clear to me though that with just a few changes a whole new world of applications opens up, and this is an opportunity not to be missed.

I THEREFORE PROPOSE the following modifications to the draft standard:

1. The renaming of the document as 'Universal Digital Interface (UDI)' Together with a recommendation that this be adopted for ALL audio applications - consumer, prosumer, and professional, where the benefits would far outweigh the slight cost of the tiny transformers needed.

2. The recognition of a new miniature UDI connector, to be developed as a matter of high priority. This would be of similar size to USB or Firewire connectors, in a flattened format suitable for PCB mounting. It should be possible to design it in male and female forms with latching, and a metal case making it almost as rugged as the XLR, but it would have the big advantage of being small enough to fit onto miniature camcorders or and similar equipment, plugged into miniature microphones suited to camcorder use, or packed with higher density into small mixing consoles or PC cards.

The use of the fully coded XLD should be optional but not preferred, and I suggest that adapter plugs (with a printed warning) no bigger than an XLR could accept the new connectors directly, providing easy connection to existing wiring.

3. The inclusion of a reference to matching digital outputs with power and optional phantom signalling.

4. A change of the DPP voltage to 8v nominal but with a permitted range of 6 to 9V, and a requirement that all microphones or other powered devices should operate correctly over this range. This permits direct powering from two-cell Lithium Ion batteries, which are increasingly the preferred power source for portable equipment such as miniature camcorders. It is of course a voltage range easily provided by NiCad or other battery sources. Note also that any voltage drops in long lines would cause no problem, given that fixed equipment would generate 8V.

5. The requirement that all UDI outputs and inputs on a device are connected directly together at the transformer centre-taps (via inductors where data separation is required) and that where a power feed is provided this is via a (shottky) diode. This provides a facility that might be called 'PowerBus' whereby any item of equipment in a digital chain may pick up power, and only one item in the chain need provide power. The diode feed eliminates any clash of voltages when multiple power sources meet. This has powerful consequences as explained later.

Note that this also brings AES42 into line with the LinDev 'UniSon' Universal Analogue Interface, which uses the same 'PowerBus' arrangement, and which I would like to offer to the AES as a proposed standard. Full details of 'UniSon' can be seen at:

http://www.lindev.com/unis.htm

6. An increase of maximum current per socket to 0.5A, and the specification of a 1A current limit, but with the proviso that a 'Total Current' figure be printed on the equipment. This would solve the problem that the specified 250mA is currently not quite enough to power a stereo 24-bit 96kHz 'podule' using available A-D convertor chips. At the same time, systems need not necessarily provide enormous total power, recognising that future A-D's will need less current. Note that the 78M08 regulator chip provides an easy source of power with current limiting above 0.5A. Chips such as the Siemans BSP452 MOSFET switch (and I am told some Maxim devices) can provide the necessary protection on battery feeds where only a few mV drop can be tolerated. Regulation from 6-8V down to clean +/-5V is easy using the MIC2951 and MAX660. 5V supplies are of course standard now for analogue as well as digital chips, and with rail to rail op-amps it is perfectly feasible to process signals up to +18dBu (balanced) with very low distortion.

7. The adoption of a more flexible signalling system in which bytes of data are not split in the very specific way currently laid down. Instead I suggest a two-character code in which the first specifies the parameter and the second its eight bit value. In particular the current gain and pre-attenuator specification should be dropped, as it is too specific and limiting, and replaced with an SPL setting.

8. In place of gain and pre-attenuator settings I propose that a single two-byte code should specify dB AL-SPL (Alignment Level Sound Pressure Level) in 1dB steps over a wide range. Thus the two-byte code S100 (100 in binary) would specify that the microphone be set so that a level of 100dB SPL should generate a digital level 18dB below Digital FS. This is in compliance with the EBU recommendation for 'Alignment Level' with 18dB of headroom. Additionally I propose that this alignment level be signalled back in the AES data as part of the signal specification. Where more headroom is required, the alignment level should simply be specified accordingly. Any use of 'pre-attenuators' should be regarded as specific to a particular source, and controlled within that source. The use of nominal SPL steps (90,100 etc) would be permitted in place of 1dB steps, in which case the source should set the most appropriate value whatever value is signalled. A whole range of similar two-byte codes would be available for future use, to be submitted by manufacturers.

9. I wonder if the use of RS232 type transmission of data at 5V pk-pk might be adopted in preference to the rather special system specified. This has the advantage that low cost microcontroller chips could then form the basis of controlled sources, with RS232 type decoding peripharals already built in (eg the PIC16C73 available for around =A33).

ADVANTAGES OF THE ABOVE SYSTEM:

1. THE TOTAL ELIMINATION OF 'MICROPHONE' SOCKETS! Any digital microphone would plug into any UDI socket directly. I envisage low cost digital microphones becoming available for only a few pounds, fully compatible with anything from a PC card input to a top mixing console.

2. THE TOTAL ELIMINATION OF 'HEADPHONE' SOCKETS! Headphones currently vary in impedance and sensitivity such that the provision of a universal headphone socket is impossible! Headphones are also quite unsuitable for stereo listening! Future headphones could plug directly into any UDI output, picking up power for an internal A-D convertor and stereo-to-binaural processor. All headphones would be calibrated to give the signalled SPL value unless locally gain controlled, and they could incorporate precise response shaping filters as well as hearing protection limiters.

3. THE TOTAL ELIMINATION OF A-D and D-A CONVERTORS!

With power available at all UDI sockets, the current practise of including analogue inputs and outputs on equipment could end. Instead, adapter leads or 'podules' could be used where needed to interface to analogue, with power simply picked up from the socket.

4. THE POSSIBILITY OF USING HIGH QUALITY MICROPHONES IN ANY APPLICATION It is currently extremely difficult to interface quality microphones to 'Prosumer' equipment such as the Sony VX1000 miniature camcorder, although such equipment is already used in broadcast production, with the next generation set to take over cinema productions! A small UDI socket on a camcorder would be all that was needed to permit input from any source, as well as a range of digital microphones or digital mic adaptors.

5. THE POSSIBILITY OF 'Source Controlled Mixing'. With 'Gain' control over a wide range (S120 to S255) it becomes possible to mix sources by simple digital addition with the gains controlled at source. This may actually offer possible noise and distortion advantages as well as permitting simple mixing in camcorders or from computer cards without the need for serious DSP.

6. ELECTRIC GUITAR USE. It is a remarkable fact that Electroacoustic guitars currently use a PP3 battery to power the mic preamp with output on a noise jack! A UDI connection would eliminate hum problems and provide power for any processing required in the instrument.

7. IN-LINE EFFECTS MODULES OR LIMITERS Simple tasks like headroom limiting between digital systems and broadcast feeds currently require a rack-mounted unit with power supply, yet they could be implemented in a small in-line podule if power were universally available from inputs and outputs. Miniature production mixers, Peak Programme Meters, Microphone HP filters, Lapel mic HF emphasis filters, Blumlien Shufflers, M-S Processors, and a whole range of serious accessories could simply plug into camcorders etc from which they would pick up their power.

8. CONTROL OF POWER AMP INSTALLATIONS Active speakers need to be turned on and off, and surround sound systems can employ numerous active speakers. The power on a UDI feed could be used to drive relays or solid state power switches to remotely turn on the locally supplied mains feed to power amps. The signalling system used for microphones could equally be used to set the gain of power amps, where similar noise optimising problems apply such that it is better to send a standard level signal to each speaker, together with an SPL AL specification, than to attempt wide digital gain control at source.

9. THE POSSIBILITY OF ABSOLUTE LEVEL operation in certain 'Purist Recording' applications where a single stereo mic is use, as well as in Psychoacoustic Experiments. With all microphones calibrated to SPL values and the Alignment SPL signalled, preservation of actual signal level from source to listener becomes possible, coupled with listener selected options for real or compressed levels.

10. THE POSSIBILITY OF COMPLEX DIRECTIONALITY CONTROL Future microphones might increasingly consist of arrays of low cost electret modules, with digital processing to control directionality or extract directional information. The current coding system puts severe limitations on the data to such units, which the new more flexible system does not.

Regards

Pete Skirrow


Robinson 2000-12-04


From: Herbie Robinson 
To: standards@aes.org
Subj: Re: Call For Comment Draft AES42

This is in reply to the Call for Comment dated September 6, 2000 on Draft AES 42, AES Standards for Acoustics - Digital Interface for Microphones.

1. I am concerned that there are no data integrity provisions for the remote control functions (A.1.1). The effect of a single bit transmission error on the Gain, Mute or Pre-Attenuation parameters would be highly likely to ruin a recording. The format should include either two parity bits or ECC bits. Any transmission errors should be reported back in page 0 of the status flag indicators (D.2) -- I would suggest page 0, byte 0.

2. I agree 100% with the comments from John Schmidt and Jim Brown, et al, on the need to mandate the fully keyed connector. Not only is there serious potential for blown up equipment, but hearing damage is a real possibility and that makes it a safely issue, too.

3. I also agree with John Schmidt that an upper limit on the current provided by the AES3-MIC receiver's power supply under fault conditions should be addressed by some some standards; however, it may already be specified by various safety standards. It would certainly be an idea to indicate that other standards will restrict this even if AES42 doesn't.

4. I have a general concern that this technology may be too immature to standardize at this point in time; however, it is necessary to have some common ground to enable the technology to develop. I don't suppose you have a beta test program for standards...


Konrath 2000-12-04

>From: SMTP%"konrath.beyerdynamic@t-online.de" 4-DEC-2000 04:26:52.53 >To: standards@aes.org >Subj: comment on AES42

Dear colleagues,

The DKE 742.6.1 group members, as principal participants in the task group that drafted the proposed task group draft for AES42-xxxx [secretariat corrections to organizational relationships], has strongly intended to get the new AES42 standard as close as possible to existing AES3-1992 standard. This has the full acceptance right from the start and is documented in 4.1. By reviewing the other comments and discussions about the connector issue, the DKE group recommends, if no consensus on the recent XLR/XLD compromise can be achieved, that we do an editorial change of eliminating all details about connector use into a strict reference to existing AES3 standard.

In fact we need to come out with AES42 standard now. It cannot be tolerated, that development of whole new product lines will be delayed by an endless standardization process. AES42 draft is in a very concrete state and a lot of hardware research had been done by members of DKE group to achieve that state.

Changing AES42 into in compliance to AES3 definitely will not work with DKE group, the connector issue has to be discussed within AES3 working group SC-02-02, where it belongs to. If there is an amendment of AES3 standard defining XLD as the new connector for example, it would be accepted by our group, but it has to be decided in SC-02-02.

Best regards,

Kai Konrath - beyerdynamic))))
chairman DKE AK742.6.1


Konrath notes 2000-12-04

[Secretariat note: the following comments were gathered from colleagues on the DKE AK742.6.1 working group by K. Konrath. They are provided here for information only. To be answerable, the individual commenters will need to submit their comments themselves. To expand the information, the secretariat has included explanations of the editorial style items.]

DKE, Mr. Goering: Clause 2, Are there any internationals standards from IEC or ISO, which could be referred to instead of AES-Standards? Check and correct reference if possible.

[Secretariat: AES style requires preference to be given to AES standards in normative references.]

DKE, Mr. Goering: Clause 2, ISO and IEC standards do not need the term Geneva CH: International Electrotechnical Commission. Delete

[Secretariat: AES follows ISO 690 bibliographical style.]

DKE, Mr. Goering: Clause 3 A clear separation between definitions and abbreviations shall be made. E. G. 3.1.9 MSB is an abbreviation and not a definition. Whereas ASCII in 3.2.1 stands for American Standard Code for Information Interchange and not for a character set. Check and correct.

[Secretariat: AES style follows the guidelines in the IEC-ISO directives that do not require separation of abbreviations and definitions except where many abbreviations may be more clear if separated. ASCII is defined as it is for the purposes of this standard only.]

NDR (large German broadcast station), Mr. Chilinski: Clause 4.2.1 to 4.2.4 There is no practical reason for using the XLD connector (I know why it has been involved). In practice there is the same fact for the analog phantom power (48V) which can destroy analog outputs in some cases. Because users should know this there is no reason for the (new) 10V phantom supply.

This new connector type has been seriously discussed in broadcasting companies. A new connector type causes confusion. Delete these subclauses.

Annex E See comment on 4.2.1 to 4.2.4. Delete.

STUDER, Mr. Lienert: Annex A Figure A.5 "IC1" and "IC 2" are exchanged (schematic versus components table) Correct.

Annex B 3rd topic "pulse width of 7 - 64 / 8 fs" - It is not clear enough that it is meaning 7 times the period 64 / 8. Clarify and correct.

Annex C Figure C.1 The D/A converter is not indicated. Amend D/A converter.


Hergesell 2000-12-06


From:   SMTP%"buero.hergesell@t-online.de"  6-DEC-2000 11:43:56.00
To: standards@aes.org
Subj: Comments on AES3-MIC (AES42)

Comments on AES3-MIC (AES42) Digitally Interfaced Microphones

On November 14, 2000, 21 members and guests participated in the discussion part of the meeting of the South German Section of the Audio Engineering Society on Digitally Interfaced Microphones in Stuttgart, Germany. The attendees ask to take the following points/proposals into account for further work:

[Secretariat note: the AESSC rules to not allow for collective comments so these comments are being accepted as those of the submitter, only, and will be so answered.]

1. Delays due to Digital Processes

The attendees are concerned on delays due to processing times in the digital signal processing unit. In order to avoid cancellation effects when using several microphones (in different modes and/or from different manufacturers) the user bits should include delay times for each microphone mode.

Alternatively, synchronization techniques similar to Internet's NTP (Network Time Protocol) should be made applicable.

2. Reception/Opening Angle

On stereophonic microphone arrays, the reception/opening angle should be included in the auxiliary data as a parameter.

3. Connector for Digitally Interfaced Microphones

Most attendees of the discussion (21) prefer maintaining the current XLR-connector without any modification (14), some prefer offering XLD-connectors additionally as an option (5), each one participant prefers XLD-connector only or the introduction of a newly-designed connector, respectively.

Jens-Helge Hergesell


Josephson replies 2001-03-15

Reply to Skirrow,

This is in response to your comments on the proposed digitally interfaced microphone standard, AES42-xxxx. I'm sure I speak for the working group and the AES Standards Committee in thanking you for the energy and efforts that you have put in toward working out the best possible standard to guide manufacturers' and audio engineers' efforts in the years to come.

We are limited in this phase of the process to replying to comments that directly address language in the Call for Comment, within the scope of the proposed standard. While your proposals are quite interesting, there is really no way to accommodate them within the digitally interfaced microphone standard as now proposed. The standards process really only functions well when interested parties lobby each other and work out a consensus. Each of the active parties behind the definition of the proposed standard has done this, along with extensive engineering analysis and field trials to prove the efficacy of their designs.

There is however movement for the definition of a new digital audio interface standard, and I encourage you to pursue your ideas as this is being discussed. We are proposing to revise the present 4.2 to refer to this work as follows, and I hope you will agree to the following revised wording for the present effort:

"Microphones and interface equipment complying with this standard should use a connector that will prevent inadvertent connection with incompatible equipment, for example, analog microphone inputs of consoles. At the time of publication of this standard, the AESSC is considering a new digital audio interface connector, which is to be suitable for digitally interfaced microphones as well. At this time the connector is the XLD, shown in annex E. If and when a new connector is defined as standard for AES3 interconnections, it shall also be used for microphones and interface equipment compliant with this standard under 4.1. In the interim, or when compatibility with existing facilities is required, the XLR-3 connector described in AES14 may be used."

We can also add a note reinforcing the requirement in 4.3 that some means shall be provided for preventing damage to analog equipment; at least warnings if the connectors are intermateable. If and when a new connector becomes standard, the working group can prepare an amendment to the standard to remove wording that becomes superfluous.

Please consider these changes and reply before 2001-03-31, with a copy to the AESSC Secretariat , whether or not this reply is acceptable to you. Of course, the AESSC procedures also point out that you may also ask us to consider your comments again for the next revision of the document. and that you may appeal the final decision to the Standards Secretariat as described in much detail in the AESSC Procedures.

Thanks and best regards, David Josephson Chair, SC-04-04

2001-03-15


Reply to Dunn,

This is in response to your comments on the proposed digitally interfaced microphone standard, AES42-xxxx. I'm sure I speak for the working group and the AES Standards Committee in thanking you for the energy and efforts that you have put in toward working out the best possible standard to guide manufacturers' and audio engineers' efforts in the years to come.

I know that you're well acquainted with the reasoning behind the various positions on the connector issue so I won't reiterate it here. There does not seem to be enough support to carry the idea of mandatory use of "safe DPP." Based on informal polls during several of the WG and task group meetings, the inadvertent application of DPP should pose no greater threat to other equipment than does standard phantom power which is typically at a higher voltage, albeit with less available current. In order to al low work to continue, I hope that you will agree to the following revised wording that would appear replacing the present 4.2:

"Microphones and interface equipment complying with this standard should use a connector that will prevent inadvertent connection with incompatible equipment, for example, analog microphone inputs of consoles. At the time of publication of this standard, the AESSC is considering a new digital audio interface connector, which is to be suitable for digitally interfaced microphones as well. At this time the connector is the XLD, shown in annex E. If and when a new connector is defined as standard for AES3 interconnections, it shall also be used for microphones and interface equipment compliant with this standard under 4.1. In the interim, or when compatibility with existing facilities is required, the XLR-3 connector described in AES14 may be used."

We can also add a note reinforcing the requirement in 4.3 that some means shall be provided for preventing damage to analog equipment; at least warnings if the connectors are intermateable.

If a new connector becomes standard, the working group can prepare an amendment to the standard to remove wording that becomes superfluous.

Please consider these changes and reply before 2001-03-31, with a copy to the AESSC Secretariat , whether or not this reply is acceptable to you. Of course, the AESSC procedures also point out that you may also ask us to consider your comments again for the next revision of the document. and that you may appeal the final decision to the Standards Secretariat as described in much detail in the AESSC Procedures.

Thanks and best regards, David Josephson Chair, SC-04-04

2001-03-15


Reply to Henkel,

This is in response to your comments on the proposed digitally interfaced microphone standard, AES42-xxxx. I'm sure I speak for the working group and the AES Standards Committee in thanking you for the energy and efforts that you have put in toward working out the best possible standard to guide manufacturers' and audio engineers' efforts in the years to come.

Nearly all of the comments you have made are editorial in nature, and after consultation with the secretariat we have adopted all of them with the exception of the revision of Table A.20. In this case, the authors of this part of the proposed standard have revised the table to show full left and full right at 100% respectively with zero to the opposite channel, and center/default being 50% to each channel, leaving the manufacturer to determine the precise values of attenuation. This removes the ambiguity you have pointed out.

Please consider these changes and reply before 2001-03-31, with a copy to the AESSC Secretariat , whether or not this reply is acceptable to you. Of course, the AESSC procedures also point out that you may also ask us to consider your comments again for the next revision of the document. and that you may appeal the final decision to the Standards Secretariat as described in much detail in the AESSC Procedures.

Thanks and best regards, David Josephson Chair, SC-04-04

2001-03-15


Reply to Hergesell,

This is in response to your comments on the proposed digitally interfaced microphone standard, AES42-xxxx. I'm sure I speak for the working group and the AES Standards Committee in thanking you for the energy and efforts that you have put in toward working out the best possible standard to guide manufacturers' and audio engineers' efforts in the years to come.

We are limited in this phase of the process to replying to comments that directly address language in the Call for Comment, within the scope of the proposed standard. We are also limited to responding to submissions from individual commenters, rather than to groups which the commenters may represent.

Your comments on inclusion of delay and stereophonic angle in the microphone data are well taken and should be the subject of a request for amendment of the proposed standard. As they would be normative, we cannot revise the presently proposed standard to include them, unless we began the whole process over again. We will include these comments however at the first opportunity to consider amendments to the proposed standard, which will probably be at the meeting in Amsterdam in May.

In order to address the concerns of other commenters, we are proposing to revise the present 4.2 as follows, and I hope you will agree to the following revised wording for the present effort:

"Microphones and interface equipment complying with this standard should use a connector that will prevent inadvertent connection with incompatible equipment, for example, analog microphone inputs of consoles. At the time of publication of this standard, the AESSC is considering a new digital audio interface connector, which is to be suitable for digitally interfaced microphones as well. At this time the connector is the XLD, shown in annex E. If and when a new connector is defined as standard for AES3 interconnections, it shall also be used for microphones and interface equipment compliant with this standard under 4.1. In the interim, or when compatibility with existing facilities is required, the XLR-3 connector described in AES14 may be used."

We can also add a note reinforcing the requirement in 4.3 that some means shall be provided for preventing damage to analog equipment; at least warnings if the connectors are intermateable.

If and when a new connector becomes standard, the working group can prepare an amendment to the standard to remove wording that becomes superfluous.

Please consider these changes and reply before 2001-03-31, with a copy to the AESSC Secretariat , whether or not this reply is acceptable to you. Of course, the AESSC procedures also point out that you may also ask us to consider your comments again for the next revision of the document. and that you may appeal the final decision to the Standards Secretariat as described in much detail in the AESSC Procedures.

Thanks and best regards, David Josephson Chair, SC-04-04

2001-03-15


Reply to Konrath,

This is in response to your comments on the proposed digitally interfaced microphone standard, AES42-xxxx. I'm sure I speak for the working group and the AES Standards Committee in thanking you for the energy and efforts that you have put in toward working out the best possible standard to guide manufacturers' and audio engineers' efforts in the years to come.

We are limited in this phase of the process to replying to comments that directly address language in the Call for Comment, within the scope of the proposed standard. In order to address the concerns of other commenters, we are proposing to revise the pre sent 4.2 as follows, and I hope you will agree to the following revised wording for the present effort:

"Microphones and interface equipment complying with this standard should use a connector that will prevent inadvertent connection with incompatible equipment, for example, analog microphone inputs of consoles. At the time of publication of this standard, the AESSC is considering a new digital audio interface connector, which is to be suitable for digitally interfaced microphones as well. At this time the connector is the XLD, shown in annex E. If and when a new connector is defined as standard for AES3 interconnections, it shall also be used for microphones and interface equipment compliant with this standard under 4.1. In the interim, or when compatibility with existing facilities is required, the XLR-3 connector described in AES14 may be used."

We can also add a note reinforcing the requirement in 4.3 that some means shall be provided for preventing damage to analog equipment; at least warnings if the connectors are intermateable.

If and when a new connector becomes standard, the working group can prepare an amendment to the standard to remove wording that becomes superfluous.

We have also received a series of editorial comments from Mr. Henkel which I believe you are aware of, including the point you discuss in annex B. Also I believe that you have agreed with the simplification of Table A.20.

Please consider these changes and reply before 2001-03-31, with a copy to the AESSC Secretariat , whether or not this reply is acceptable to you. Of course, the AESSC procedures also point out that you may also ask us to consider your comments again for the next revision of the document. and that you may appeal the final decision to the Standards Secretariat as described in much detail in the AESSC Procedures.

Thanks and best regards, David Josephson Chair, SC-04-04

2001-03-15


Reply to Olson,

This is in response to your comments on the proposed digitally interfaced microphone standard, AES42-xxxx. I'm sure I speak for the working group and the AES Standards Committee in thanking you for the energy and efforts that you have put in toward working out the best possible standard to guide manufacturers' and audio engineers' efforts in the years to come.

I know that you're well acquainted with the reasoning behind the various positions on the connector issue so I won't reiterate it here. There does not seem to be enough support to carry the idea of mandatory use of the XLD connector at this time. There is ongoing work on the topic, and with that in mind I hope that you will agree to the following revised wording that would appear replacing the present 4.2:

"Microphones and interface equipment complying with this standard should use a connector that will prevent inadvertent connection with incompatible equipment, for example, analog microphone inputs of consoles. At the time of publication of this standard, the AESSC is considering a new digital audio interface connector, which is to be suitable for digitally interfaced microphones as well. At this time the connector is the XLD, shown in annex E. If and when a new connector is defined as standard for AES3 interconnections, it shall also be used for microphones and interface equipment compliant with this standard under 4.1. In the interim, or when compatibility with existing facilities is required, the XLR-3 connector described in AES14 may be used."

We can also add a note reinforcing the requirement in 4.3 that some means shall be provided for preventing damage to analog equipment; at least warnings if the connectors are intermateable.

If and when a new connector becomes standard, the working group can prepare an amendment to the standard to remove wording that becomes superfluous.

Please consider these changes and reply before 2001-03-31, with a copy to the AESSC Secretariat , whether or not this reply is acceptable to you. Of course, the AESSC procedures also point out that you may also ask us to consider your comments again for the next revision of the document. and that you may appeal the final decision to the Standards Secretariat as described in much detail in the AESSC Procedures.

Thanks and best regards, David Josephson Chair, SC-04-04

2001-03-15


Reply to Paul,

This is in response to your comments on the proposed digitally interfaced microphone standard, AES42-xxxx. I'm sure I speak for the working group and the AES Standards Committee in thanking you for the energy and efforts that you have put in toward working out the best possible standard to guide manufacturers' and audio engineers' efforts in the years to come.

The comments you have made are entirely editorial in nature and I have passed them on to the secretariat for inclusion in editing the final document. I'm not certain what the criteria are for determining the order in which patents are listed but your request along with the address correction will be considered. SGS has been contacted with regard to the AES patent agreement; as far as I know they have not yet responded.

With regard to including parts manufactured by your company in the hardware examples, I think this is probably unwarranted given that no other manufacturers are listed. Your point about AES3 is well taken and we will include a reference to the fact that the transformer must meet AES3 requirements but with a center tap, and must meet those requirements while passing DPP current through the center tap.

Please consider these changes and reply before 2001-03-31, with a copy to the AESSC Secretariat , whether or not this reply is acceptable to you. Of course, the AESSC procedures also point out that you may also ask us to consider your comments again for the next revision of the document. and that you may appeal the final decision to the Standards Secretariat as described in much detail in the AESSC Procedures.

Thanks and best regards, David Josephson Chair, SC-04-04

2001-03-15


Reply to Rayburn,

This is in response to your comments on the proposed digitally interfaced microphone standard, AES42-xxxx. I'm sure I speak for the working group and the AES Standards Committee in thanking you for the energy and efforts that you have put in toward working out the best possible standard to guide manufacturers' and audio engineers' efforts in the years to come.

I know that you're well acquainted with the reasoning behind the various positions on the connector issue so I won't reiterate it here. There does not seem to be enough support to carry the idea of mandatory use of the XLD connector at this time. There is ongoing work on the topic, and with that in mind I hope that you will agree to the following revised wording that would appear replacing the present 4.2:

"Microphones and interface equipment complying with this standard should use a connector that will prevent inadvertent connection with incompatible equipment, for example, analog microphone inputs of consoles. At the time of publication of this standard, the AESSC is considering a new digital audio interface connector, which is to be suitable for digitally interfaced microphones as well. At this time the connector is the XLD, shown in annex E. If and when a new connector is defined as standard for AES3 interconnections, it shall also be used for microphones and interface equipment compliant with this standard under 4.1. In the interim, or when compatibility with existing facilities is required, the XLR-3 connector described in AES14 may be used."

We can also add a note reinforcing the requirement in 4.3 that some means shall be provided for preventing damage to analog equipment; at least warnings if the connectors are intermateable.

If and when a new connector becomes standard, the working group can prepare an amendment to the standard to remove wording that becomes superfluous.

Please consider these changes and reply before 2001-03-31, with a copy to the AESSC Secretariat , whether or not this reply is acceptable to you. Of course, the AESSC procedures also point out that you may also ask us to consider your comments again for the next revision of the document. and that you may appeal the final decision to the Standards Secretariat as described in much detail in the AESSC Procedures.

Thanks and best regards, David Josephson Chair, SC-04-04

2001-03-15


Reply to Robinson,

This is in response to your comments on the proposed digitally interfaced microphone standard, AES42-xxxx. I'm sure I speak for the working group and the AES Standards Committee in thanking you for the energy and efforts that you have put in toward working out the best possible standard to guide manufacturers' and audio engineers' efforts in the years to come.

We are limited in this phase of the process to replying to comments that directly address language in the Call for Comment, within the scope of the proposed standard. The idea of parity or ECC for confidence checking the remote control instructions is a good one and should be submitted as an amendment to the standard if and when it is released.

With regard to the connector choice, there does not seem to be enough support to mandate the use of the XLD connector. There is however movement for the definition of a new digital audio interface standard embodying a new connector, and I encourage you to pursue your ideas as this is being discussed. We are proposing to revise the present 4.2 to refer to this work as follows, and I hope you will agree to the following revised wording for the present effort:

"Microphones and interface equipment complying with this standard should use a connector that will prevent inadvertent connection with incompatible equipment, for example, analog microphone inputs of consoles. At the time of publication of this standard, the AESSC is considering a new digital audio interface connector, which is to be suitable for digitally interfaced microphones as well. At this time the connector is the XLD, shown in annex E. If and when a new connector is defined as standard for AES3 interconnections, it shall also be used for microphones and interface equipment compliant with this standard under 4.1. In the interim, or when compatibility with existing facilities is required, the XLR-3 connector described in AES14 may be used."

We can also add a note reinforcing the requirement in 4.3 that some means shall be provided for preventing damage to analog equipment; at least warnings if the connectors are intermateable.

If and when a new connector becomes standard, the working group can prepare an amendment to the standard to remove wording that becomes superfluous.

With regard to your comment about immature technology, in fact there is a "beta test" program for standards; it's called a trial use document. The Steering Committee of the AESSC after reviewing the comments may choose to adopt this as a trial use standard rather than a full standard.

Please consider these changes and reply before 2001-03-31, with a copy to the AESSC Secretariat , whether or not this reply is acceptable to you. Of course, the AESSC procedures also point out that you may also ask us to consider your comments again for the next revision of the document. and that you may appeal the final decision to the Standards Secretariat as described in much detail in the AESSC Procedures.

Thanks and best regards, David Josephson Chair, SC-04-04

2001-03-15


Reply to Schmidt,

This is in response to your comments on the proposed digitally interfaced microphone standard, AES42-xxxx. I'm sure I speak for the working group and the AES Standards Committee in thanking you for the energy and efforts that you have put in toward working out the best possible standard to guide manufacturers' and audio engineers' efforts in the years to come.

I know that you're well acquainted with the reasoning behind the various positions on the connector issue so I won't reiterate it here. Based on your agreement in the telephone conference of December 20, we are proposing the the following revised wording replacing the present 4.2:

"Microphones and interface equipment complying with this standard should use a connector that will prevent inadvertent connection with incompatible equipment, for example, analog microphone inputs of consoles. At the time of publication of this standard, the AESSC is considering a new digital audio interface connector, which is to be suitable for digitally interfaced microphones as well. At this time the connector is the XLD, shown in annex E. If and when a new connector is defined as standard for AES3 interconnections, it shall also be used for microphones and interface equipment compliant with this standard under 4.1. In the interim, or when compatibility with existing facilities is required, the XLR-3 connector described in AES14 may be used."

We can also add a note reinforcing the requirement in 4.3 that some means shall be provided for preventing damage to analog equipment; at least warnings if the connectors are intermateable.

If and when a new connector becomes standard, the working group can prepare an amendment to the standard to remove wording that becomes superfluous.

In response to your comment about short circuit current, I believe that it is the intent of the authors of the "DPP" standard that current be limited to the maximum specified, i. e. 300 mA. To clarify this clause, I propose this language to be added to the second sentence of the second paragraph of 5.1, and I hope you will agree with it:

"that is, the voltage source shall be current-limited to supply no more than 300 mA through any combination of pins at the microphone interface."

Please consider these changes and reply before 2001-03-31, with a copy to the AESSC Secretariat , whether or not this reply is acceptable to you. Of course, the AESSC procedures also point out that you may also ask us to consider your comments again for the next revision of the document. and that you may appeal the final decision to the Standards Secretariat as described in much detail in the AESSC Procedures.

Thanks and best regards, David Josephson Chair, SC-04-04

2001-03-15


Reply to Brown,

This is in response to your comments on the proposed digitally interfaced microphone standard, AES42-xxxx. I'm sure I speak for the working group and the AES Standards Committee in thanking you for the energy and efforts that you have put in toward working out the best possible standard to guide manufacturers' and audio engineers' efforts in the years to come.

In addressing your comments both written and over the course of your participation in meetings, I note that much of your concern refers to issues pertaining to the provision of microphone cabling in a facility. While this is an admirable target for engineering improvement, it is not within the scope of the present Call for Comment. The issues pertaining to interface at the microphone body and at the equipment controlling it are quite different from those in, for example, a patch bay. I doubt that you would find much support for requiring a unique connector in a patch bay.

I know that you're well acquainted with the reasoning behind the various positions on the connector issue so I won't reiterate it here. There does not seem to be enough support to carry the idea of mandatory use of the XLD connector. Based on your agreement in the telephone conference of 2000-12-20, we propose the following revised wording that would appear replacing the present 4.2:

"Microphones and interface equipment complying with this standard should use a connector that will prevent inadvertent connection with incompatible equipment, for example, analog microphone inputs of consoles. At the time of publication of this standard, the AESSC is considering a new digital audio interface connector, which is to be suitable for digitally interfaced microphones as well. At this time the connector is the XLD, shown in annex E. If and when a new connector is defined as standard for AES3 interconnections, it shall also be used for microphones and interface equipment compliant with this standard under 4.1. In the interim, or when compatibility with existing facilities is required, the XLR-3 connector described in AES14 may be used."

We can also add a note reinforcing the requirement in 4.3 that some means shall be provided for preventing damage to analog equipment; at least warnings if the connectors are intermateable.

If and when a new connector becomes standard, the working group can prepare an amendment to the standard to remove wording that becomes superfluous.

Please consider these changes and reply before 2001-03-31, with a copy to the AESSC Secretariat , whether or not this reply is acceptable to you. Of course, the AESSC procedures also point out that you may also ask us to consider your comments again for the next revision of the document. and that you may appeal the final decision to the Standards Secretariat as described in much detail in the AESSC Procedures.

Thanks and best regards, David Josephson Chair, SC-04-04

2001-03-15


Secretariat summary 2001-04-05

[The following editorial wording change has been agreed upon for the annex that is now referenced by subclause 4.2.]

Annex F
(normative)

Cable connector for AES-MIC

The connector to be used by microphones and interface equipment complying with this standard is under consideration in the AESSC.

NOTE: While this standard requires full compatibility with AES3, equipment complying with this standard may use a connector that will prevent inadvertent connection with incompatible equipment, for example, analog microphone inputs of consoles. If and when a new connector is defined as standard for AES3 interconnections, it shall also be permitted to be used for microphones and interface equipment compliant with this standard under 4.1. When compatibility with other facilities is required, the XLR-3 connector described in AES14 can be used.

[The remaining subclauses in clause 4 are now appended to the annex.]

If an alternative connector is used, for example, to prevent mating with XLR connectors, that connector shall be the XLD connector described in annex E.

The XLD connector and associated wiring shall include a zebra ring. The color pattern on the ring shall be black-white-black- white for ease of recognition in low light environments. The ring shall have a rough surface (bumps) to facilitate tactile feedback to the user. An example of the zebra ring is shown in annex E.

The presence of the zebra ring on the XLD connector shall indicate that it carries a digital audio signal, that it may be carrying power, and that its associated circuitry cannot be damaged if power is applied in compliance with this standard.

The presence of the zebra ring on the associated cable indicates that the cable is intended for transmission of digital signals.


The comment period is closed and the document is published.

For more information about standards activity: standards@aes.org

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