Schmidt 2000-09-19
Fro To: [email protected]
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
From: SMTP%"[email protected]" 22-SEP-2000 17:31:41.42
To: "[email protected]"
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.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.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.
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
From: SMTP%"[email protected]" 22-SEP-2000 20:04:30.14
To:
Subj: Call for Comment Draft AES42
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
From: SMTP%"[email protected]" 23-SEP-2000 03:33:37.68I agree with the thrust of the comments by John Schmidt submitted 2000-09-19, and Jim Brown submitted 2000-09-22.
To: [email protected]
Subj: Draft AES42-xxxx CFC
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 [email protected]
From: SMTP%"[email protected]" 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
From: SMTP%"[email protected]" 30-SEP-2000 15:53:22.13Dear Madams, dear Sirs,
To: AESSC Secretariat
Subj: DRAFT AES42-xxxx Comments
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 BalanceThe left channel is calculated there by (
-----------------------------------------------------------------
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
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 BalanceThe left channel is calculated there by (
-----------------------------------------------------------------
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
* 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:
[email protected]
From: SMTP%"[email protected]" 24-DEC-2000 17:51:17.38
To: [email protected]
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
Thanks and best regards,
David Josephson
Chair, SC-04-04
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: 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
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
Thank you for your kind consideration of these items. With Kind
Regards, Jon Paul
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
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...
>From: SMTP%"[email protected]" 4-DEC-2000 04:26:52.53 >To:
[email protected] >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))))
[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.
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.
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
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 Thanks and best
regards, David Josephson Chair, SC-04-04 2001-03-15 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 Thanks
and best regards, David Josephson Chair, SC-04-04 2001-03-15 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 Thanks and best regards, David Josephson Chair, SC-04-04 2001-03-15
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 Thanks
and best regards, David Josephson Chair, SC-04-04 2001-03-15 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
Thanks and best regards, David
Josephson Chair, SC-04-04 2001-03-15 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 Thanks and best
regards, David Josephson Chair, SC-04-04 2001-03-15 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 Thanks and best
regards, David Josephson Chair, SC-04-04 2001-03-15 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 Thanks
and best regards, David Josephson Chair, SC-04-04 2001-03-15 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 Thanks and best regards, David Josephson Chair, SC-04-04 2001-03-15
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 Thanks and best
regards, David Josephson Chair, SC-04-04 2001-03-15 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 Thanks and best regards, David Josephson Chair,
SC-04-04 2001-03-15
[The following editorial wording change has been agreed upon for the annex
that is now referenced by subclause 4.2.] 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.]
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.
For more information about standards activity: [email protected]
Paul 2000-11-14
From: SMTP%"[email protected]" 14-NOV-2000 16:17:30.05
To: [email protected]
CC: [email protected]
Subj: Call for comment DRAFT AES42-xxxx: Patents, Phantom Power
Transformers
Jon D. Paul, V.P.=09
Scientific Conversion, Inc.
42 Truman Drive Novato, CA 94947 USA
Web
[email protected]
telephone +001-415-892-2323 fax: +001-415-892-2321
Ratio 1:1 center tap
3/ Page 18, partslist, TR1: "transformer according to AES3, 6.1" same comment
as above.
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
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
Skirrow 2000-11-25
From: SMTP%"[email protected]" 25-NOV-2000 13:23:17.19
To: [email protected]
Subj: call for comments - draft AES42
Robinson 2000-12-04
From: Herbie Robinson
To: [email protected]
Subj: Re: Call For Comment Draft AES42
Konrath 2000-12-04
chairman DKE AK742.6.1
Konrath notes
2000-12-04
[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.
Hergesell 2000-12-06
From: SMTP%"[email protected]" 6-DEC-2000 11:43:56.00
To: [email protected]
Subj: Comments on AES3-MIC (AES42)
Josephson replies
2001-03-15
Reply to Dunn,
Reply to Henkel,
Reply to Hergesell,
Reply to Konrath,
Reply to Olson,
Reply to
Paul,
Reply to
Rayburn,
Reply to Robinson,
Reply to Schmidt,
Reply to
Brown,
Secretariat summary 2001-04-05
Annex F
(normative)
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 comment period is closed and the document is published.
(C) 1999, Audio Engineering Society, Inc.