Comments on DRAFT AES59-xxxx

last updated 2010-03-22

Comments to date on DRAFT AES59-xxxx, AES standard for professional audio - Audio application of 25-way D-type connectors in balanced circuits ,
published 2009-12-08 for comment.


Comment received from Graham Hinton, 2009-12-08

One point I disagree with:

"4.1 Connector gender Connectors on free cables shall be male (pin) type."

I would not recommend the use of back to back female-female gender changers. Most such devices are intended for RS232 bodging, not 110 ohm impedance matching. For analogue audio a connecting cable is unidirectional and male to male wired pin for pin. For digital audio the cable is bidirectional (4 pairs each way) and a male to male cable has to be wired with inputs and outputs crossed over. A female to male pin for pin extension cable should not be precluded.

This difference means that digital cables cannot be used for analogue applications and should be distinguished. Even an XLR breakout would be different: either 8 x male or 8 x female for analogue and 4 male + 4 female for digital. There is a confusion about using digital cable for analogue: the cable type is perfectly capable and sometimes cheaper, but a made up loom would be incorrect. I would recommend a standard labelling to identify and distinguish similar looking cable assemblies.

Reply from Ray A. Rayburn, 2010-01-25

Thanks for your comments. You caught something the working group missed. We propose to fix this by making the following editorial changes:

  1. 4.1; second para; second sentence. Add the words, "Straight-through" before the words "interconnect cables";
  2. 4.1; new NOTE 2. "Direct digital interconnects between equipment will require a crossover arrangement to connect the transmitter outputs of one connector to the receiver inputs of the other, and vice versa."

By keeping the changes on the level of editorial clarifications rather than a wholesale re-write of the section, we will not have to withdraw and re-issue the document with a new call for comment period.

I hope this change satisfies your concerns. Thank you for making this a better document.

Sincerely,

Ray A. Rayburn - chair SC-05

Comment received from Graham Hinton, 2009-01-26

I'm quite happy with stating that equipment connectors SHALL be female. (I certainly want to avoid introducing more variables.) The second sentence and the whole second paragraph are confusing and the original Note is just plain wrong armchair engineering.

So that just leaves one sentence and a new note. Having stated that the equipment is only female it is implicit that the mating cable connector is male. It is not necessary to say anything about the other end of the cable which would be dictated by its application.

As I see it there are:

  1. Like to like connection cables. These would be male to male, but analogue and digital are wired differently (digital being crossover) so the two are not interchangeable and should be labelled Analogue or Digital on the connector shell
  2. Extension cables. These would be male to female and (coincidentally) digital 110 ohm cable may be use for analogue, but not vice versa.
  3. Breakout cables. These would be male D-type to any other audio connector which could be male or female. For the XLR subset analogue and digital are not interchangeable.
  4. Patch boxes and panels. These would have female D-types. Analogue and digital are not interchangeable. If you connect two digital crossover cables a third crossover is also needed here to give a single crossover overall. [This is what a female to female adapter means, but it needs to be explained so that the back to back types are not assumed.]

I think if would be helpful if the notes discussed the above and gave a rationale and recommended practise. The more variables there are results in confusion and possible damage to equipment due to incorrect use.

The reason I object to the note is that the most likely damage to a D-type will occur when a pair are mated, caused by a knock or the strain of supporting the weight of an audio type multicore (especially with eight mated XLRs on it). Pins may be bent straight, but socket contacts get stretched and become intermittent. This makes equipment vulnerable and possibly a write-off, cheaper to replace than repair. The answer is not in the connector gender, but in supporting the cable properly to prevent damage in the first place and I suggest that the note should recommend the use of cable tie bars, preferably built as part of the equipment.

I think it is important to recommend that all equipment connectors and cables adopting this standard be clearly labelled as "AES59 Analogue" or "AES59 Digital" (or just AES59-A and AES59-D to prevent arguments about spelling) to make it clear that this is NOT prior similar, but incompatible usages. There are over fifteen years worth of Tascam equipment with M2.6 screwlocks and digital equipment with the Yamaha format in the field that are not compatible.

best regards
Graham Hinton
Hinton Instruments

Reply from Ray A. Rayburn, 2010-03-17

Mr. Hinton - You wrote:

"I'm quite happy with stating that equipment connectors SHALL be female. (I certainly want to avoid introducing more variables.) The second sentence and the whole second paragraph are confusing and the original Note is just plain wrong armchair engineering.

"So that just leaves one sentence and a new note.

"Having stated that the equipment is only female it is implicit that the mating cable connector is male. It is not necessary to say anything about the other end of the cable which would be dictated by its application."

It may not have been necessary to state that the cable end connector is male, but it is not incorrect to so state. In the interests of passing a Standard, I don't see any need to change this. The verbs in the second paragraph and Note are both "may" which makes them not a requirement.

You wrote:

"1) Like to like connection cables. These would be male to male, but analogue and digital are wired differently (digital being crossover) so the two are not interchangeable and should be labelled Analogue or Digital on the connector shell"

We had already agreed to add a NOTE 2 under 4.1:

NOTE 2. Direct digital interconnects between equipment will require a crossover arrangement to connect the transmitter outputs of one connector to the receiver inputs of the other, and vice versa.

The Standard does not address marking of cables or connectors. The Scope says:

"This standard specifies a contact assignment and gender for 25-contact D-type connectors used to connect multiple audio signals in balanced analogue or AES3 digital form. This document shall not consider the suitability of connector and cable types for specific applications. This document shall not consider issues of safety."

You wrote about:
"2) Extension cables. ..."
"3) Breakout cables. ..."
"4) Patch boxes and panels. ..."
"I think if would be helpful if the notes discussed the above and gave a rationale and recommended practise. The more variables there are results in confusion and possible damage to equipment due to incorrect use."

"The reason I object to the note is that the most likely damage to a D-type will occur when a pair are mated, caused by a knock or the strain of supporting the weight of an audio type multicore (especially with eight mated XLRs on it). Pins may be bent straight, but socket contacts get stretched and become intermittent. This makes equipment vulnerable and possibly a write-off, cheaper to replace than repair. The answer is not in the connector gender, but in supporting the cable properly to prevent damage in the first place and I suggest that the note should recommend the use of cable tie bars, preferably built as part of the equipment."

All of these issues are outside of the Scope of this Standard.

It might be a worthwhile project, however, to produce a document on implementation details using these connectors. Would you be willing to write a first draft for the Working Group?

You wrote:

"I think it is important to recommend that all equipment connectors and cables adopting this standard be clearly labelled as "AES59 Analogue" or "AES59 Digital" (or just AES59-A and AES59-D to prevent arguments about spelling) to make it clear that this is NOT prior similar, but incompatible usages. There are over fifteen years worth of Tascam equipment with M2.6 screwlocks and digital equipment with the Yamaha format in the field that are not compatible."

Again this is something that is outside the scope of the Standard as written. It would fit well into a companion document on suggested implementation details. If the Working Group feels strongly about the marking issue the Scope could be expanded in the next revision.

Because the comment period is now closed, please reply within 14 days if this reply is not acceptable to you. You may also ask us to consider your comments again for the next revision of the document. You may also appeal our decision to the Standards Secretariat.

Thanks for your comments.

Ray A. Rayburn - chair SC-05-02

Comment received from Chris Gaunt, 2009-03-04

We have several comments to make:

1) The title of the standard: We feel that, whist technically correct, this will give the false impression that the AES has standardized on the use of 25-way D- type connectors for (multi-circuit) balanced audio. We fear that customers will in the future demand that we use these connectors for multi-circuit balanced audio.

For analogue audio, we prefer the use of 37-way D-type connectors, because of their better crosstalk performance, and for several months prior to this call for comment, we have been designing a product which uses these connectors.

We suggest that the title is changed to: Audio application of 25-way D-type connectors when used in balanced circuits.

2) We are not happy about the standardization of the connector on the equipment being female. We believe that the gender should not be standardized.

We prefer the convention that outputs are on male and inputs are on female connectors, and the product that we have been designing does this. Our preference is in line with the AES standard for the XLR-3 with AES3.

The proposed standard gives an example of maintainability as the only reason for having all panel connectors female. However, if all panels are female, we believe that there is a danger of incorrect plugging (output to output, input to input) and that this is a more important issue.

Also, we do not think there should be phantom voltages (AES42 or Mic inputs) on male connectors, which would be a consequence of making all panel connectors female, if these circuits were implemented using this standard. Regarding maintainability: In our experience, it is the female connectors that reach the end of their life first, because the contacts tend to splay with multiple insertions.

Also, we are aware of an e-mail from the SC-05-02 reflector, dated 30-10-09, concerning miniature XL type connectors. Although these are not the same as 25-way D-type connectors, there are similar issues of maintainability. In the e-mail it is reported that one industry uses chassis male, cable female, because ?it is just too easy for dirt, sand, or other small objects to become lodged in the female contacts requiring in some cases replacement of the connector. By using the female version of the connector exclusively on the cable ends the need to take a piece of equipment out of service for repairs is eliminated, and they merely have to repair or replace a cable end.?

This supports our belief that the sometimes conflicting issues of simplicity of connection and maintainability should be left up to each manufacturer/industry.

Also, standardization of the gender convention is not as necessary for successful interoperation as standardization of the pin out. Please also see comment 3.

3) We are not happy about the standardization of digital connections having 4 circuits for RCV and 4 for XMT. We believe it should be allowable to have 8 RCV or 8 XMT on a connector, and the product that we have been designing does this.

Although section 4.2.2 only says that digital connections ?should? provide 4 RCV and 4 XMT, the second paragraph says that the connector designations "shall? be as in table 2, which shows 4 RCV and 4 XMT.

AES3 circuits can easily be provided with either all RCV or all XMT, utilising FPGA (Field Programmable Gate Array) designs, or dedicated hardware. Our experience, with mixing consoles, is that customers require more inputs than outputs so we would like to have modules that are just inputs or just outputs. If the standard allows only 4 RCV or XMT on a connector, manufacturers will end up providing twice as many connectors, with half of each wasted.

We note that Wheatstone have existing digital I/O products where there are 8 RCV or 8 XMT on 25-way D-type connectors (although they have chosen to use female on the panel and the pin out complies with AES59 if you ignore the RCV/XMT designation of table 2).

Also, by combining comments 2 & 3, we can provide 8 RCV on a female panel connector and 8 XMT on a male panel connector. This removes the need for crossover cables and better fits with the AES3 standard for XLR-3 connectors.

We can suggest wording changes for comments 2 & 3, but they will obviously be extensive. If these comments are not rejected, perhaps we can do this within SC-05-02?

Whilst these comments would reduce the scope of AES59, we feel it will still be a worthwhile standard.

4) In section 4.3.2, it states that ?The jackscrew thread shall be described in the accompanying documentation?. We are not sure what accompanying documentation is being referred to. Is this accompanying documentation to the standard? Or, is it accompanying documentation for the product?

Sincerely, Chris Gaunt
Calrec Audio Ltd.

Reply from Ray A. Rayburn, 2010-03-17

[quoted text in italics]
Mr. Gaunt -

To set some background, the Standards that AES publishes are voluntary. They are not regulations. Those who wish can follow AES Standards and those who wish can ignore any or all of them.

The Scope of the Standard sets the limits of what it is trying to address. In general I have found it is easier to pass Standards with narrowly defined Scopes, and hopefully the narrow scope will allow for wider adoption of the Standard. In this case the Scope says:

"This standard specifies a contact assignment and gender for 25-contact D-type connectors used to connect multiple audio signals in balanced analogue or AES3 digital form. This document shall not consider the suitability of connector and cable types for specific applications. This document shall not consider issues of safety."

You wrote:

"1) The title of the standard: We feel that, whist technically correct, this will give the false impression that the AES has standardized on the use of 25-way D-type connectors for (multi-circuit) balanced audio. We fear that customers will in the future demand that we use these connectors for multi-circuit balanced audio."

Read the Scope again. _If_ someone has decided to use "25-way D-type connectors" instead of DL or Varicon or some other option, we hope they will follow this Standard. This Standard was written because several different manufacturers were using these connectors in incompatible ways, and we hope to reduce the amounts of similar but incompatible connectors in use. In no way should this Standard be seen as suggesting that this connector is better than others available.

"For analogue audio, we prefer the use of 37-way D-type connectors, because of their better crosstalk performance, and for several months prior to this call for comment, we have been designing a product which uses these connectors."

This Standard does not indicate that use of the 37-way D-type connectors or any other connector is inappropriate. Note for example that AES-2id shows a contact assignment using a 50-way D-type connector but says:

[AES-2id-2006] "The suggested 50-contact D-subminiature type connector shown in figure 7.3 does not preclude the use of any other multi-contact connector that may be better suited to specific applications. If, however, this connector is selected, the contact arrangement shown in table 7.1 should be used to ensure compatible connections between different equipments."

You wrote:

"We suggest that the title is changed to: Audio application of 25-way D-type connectors when used in balanced circuits."

AES59 is a Standard, not an application note. It provides a standardized interconnect for those who decide to follow it.

"We are not happy about the standardization of the connector on the equipment being female. We believe that the gender should not be standardized.

"We prefer the convention that outputs are on male and inputs are on female connectors, and the product that we have been designing does this."

There is no requirement to follow this or any other AES Standard.

"Our preference is in line with the AES standard for the XLR-3 with AES3."

These are very different connectors. They do not have to follow a common convention.

"The proposed standard gives an example of maintainability as the only reason for having all panel connectors female. However, if all panels are female, we believe that there is a danger of incorrect plugging (output to output, input to input) and that this is a more important issue."

Incorrect connections will not function. There is no requirement to follow this or any other AES Standard.

"Also, we do not think there should be phantom voltages (AES42 or Mic inputs) on male connectors, which would be a consequence of making all panel connectors female, if these circuits were implemented using this standard."

This Standard does not address any sort of phantom power. It is outside the Scope of the Standard.

While I do not believe male contacts with phantom power applied are a safety issue, the Scope of the Standard says:

"This document shall not consider issues of safety."

You wrote:

"Regarding maintainability: In our experience, it is the female connectors that reach the end of their life first, because the contacts tend to splay with multiple insertions.

"Also, we are aware of an e-mail from the SC-05-02 reflector, dated 30-10-09, concerning miniature XL type connectors. Although these are not the same as 25-way D-type connectors, there are similar issues of maintainability. In the e-mail it is reported that one industry uses chassis male, cable female, because "it is just too easy for dirt, sand, or other small objects to become lodged in the female contacts requiring in some cases replacement of the connector. By using the female version of the connector exclusively on the cable ends the need to take a piece of equipment out of service for repairs is eliminated, and they merely have to repair or replace a cable end."

These are very different connectors. They do not have to follow a common convention.

"This supports our belief that the sometimes conflicting issues of simplicity of connection and maintainability should be left up to each manufacturer/industry.

"Also, standardization of the gender convention is not as necessary for successful interoperation as standardization of the pin out."

This Standard was proposed because the industry had failed to resolve incompatible ways of using this connector.

"We are not happy about the standardization of digital connections having 4 circuits for RCV and 4 for XMT. We believe it should be allowable to have 8 RCV or 8 XMT on a connector, and the product that we have been designing does this."

Compliance with the Standard is voluntary. I myself have designed equipment that used this connector for multiple AES3 circuits with 8 RCV or 8 XMT on a connector.

"Although section 4.2.2 only says that digital connections "should" provide 4 RCV and 4 XMT, the second paragraph says that the connector designations "shall" be as in table 2, which shows 4 RCV and 4 XMT."

This is intentional to acknowledge that 4 RCV + 4 XMT are not always appropriate, but to insist that if you say a connection is AES59 compliant then it must follow Table 2.

"AES3 circuits can easily be provided with either all RCV or all XMT, utilising FPGA (Field Programmable Gate Array) designs, or dedicated hardware. Our experience, with mixing consoles, is that customers require more inputs than outputs so we would like to have modules that are just inputs or just outputs. If the standard allows only 4 RCV or XMT on a connector, manufacturers will end up providing twice as many connectors, with half of each wasted."

That is fine, just don't claim AES59 compliance.

"We note that Wheatstone have existing digital I/O products where there are 8 RCV or 8 XMT on 25-way D-type connectors (although they have chosen to use female on the panel and the pin out complies with AES59 if you ignore the RCV/XMT designation of table 2).

"Also, by combining comments 2 & 3, we can provide 8 RCV on a female panel connector and 8 XMT on a male panel connector. This removes the need for crossover cables and better fits with the AES3 standard for XLR-3 connectors."

There is no requirement to follow this or any other AES Standard.

"We can suggest wording changes for comments 2 & 3, but they will obviously be extensive. If these comments are not rejected, perhaps we can do this within SC-05-02?"

We would welcome suggested detailed wording to improve the next revision of this document.

"In section 4.3.2, it states that "The jackscrew thread shall be described in the accompanying documentation". We are not sure what accompanying documentation is being referred to. Is this accompanying documentation to the standard? Or, is it accompanying documentation for the product?"

This is a requirement that if the manufacturer claims AES59 compliance, they must also specify the jackscrew threading in their documentation. This should make it more likely that the user buys the correct thing when ordering connectors to use with a product.

Because the comment period is now closed, please reply within 14 days if this reply is not acceptable to you. You may also ask us to consider your comments again for the next revision of the document. You may also appeal our decision to the Standards Secretariat.

Ray A. Rayburn - chair SC-05-02

Comment received from Chris Gaunt, 2009-03-31

Mr. Rayburn

We are very disappointed with your response to all bar the 4th of our comments. It seems we have totally different views of how Standards are used in practice. Yes, AES Standards are, technically, voluntary. However, the AES is held in high regard and its Standards are valued and relied upon by the industry. These are some of the reasons why Calrec is a Sustaining Member of the AES and has been for many years. I think we understand our market of Live Television Broadcast very well, having sold into it for over 30 years. Our customers like Standards and when they decide to adopt one, it ceases to be voluntary for any manufacturer who wishes to supply goods to them. If this Standard is published in its current form, it is likely to materially affect Calrec's business.

You wrote:

"There is no requirement to follow this or any other AES Standard."

This is simply not true. Our customers require us to follow many AES and other Standards.

The main thrust of your response seems to be that AES59 is one way of using the 25-way D-type connector but other ways are possible providing that AES59 compliance is not claimed. I am not a Standards expert: Are you saying that we could propose another Standard for the use of this connector for the same purpose, but with different gender and circuit use? In your opinion, do you think this would be acceptable to the AES?

If this is the case, then AES59 should not be published until the alternative Standard is ready to be published and, even then, some amendments will be necessary. If it is not the case and if AES59 cannot incorporate options for the use of the connector, then no Standard should be published.

We do not think that there is any point in responding to all of your comments individually here. In general, you have dismissed many of our arguments as not being relevant either because they refer to different connectors or are outside the scope of AES59. However, we still think the issues we have raised are relevant.

There are some specific points though:

We wrote:

"We suggest that the title is changed to: Audio application of 25-way D-type connectors when used in balanced circuits."

You wrote:

"AES59 is a Standard, not an application note."

We did not add the word "application" to the title. We added "when used" to help people understand that the AES is not saying you must use 25-way D-type connectors for balanced audio. We do not think that adding "when used" changes the meaning of the word "application" nor does it degrade the title in any way. It merely makes it clearer what is intended. You should think how someone without your experience of dealing with Standards will read the title. They may not read the scope at all. You know what the title is meant to mean but less knowledgeable people could interpret it differently. If the title is not changed it is likely to put us in the difficult position of trying to persuade a potential customer that they have read it wrongly.

We wrote:

"Regarding maintainability: In our experience, it is the female connectors that reach the end of their life first, because the contacts tend to splay with multiple insertions."

You did not respond to this. The reason given in AES59 for having female connectors on the panel is no more valid than this. Yes, this is just what's been decided for AES59. However, as we've said, if that's the only Standard for the use of these connectors, our customers are likely to mandate that we follow it.

We wrote:

"Also, standardization of the gender convention is not as necessary for successful interoperation as standardization of the pin out."

You wrote:

"This Standard was proposed because the industry had failed to resolve incompatible ways of using this connector."

It is not one industry. There are different sectors that have different requirements. If everything is labelled, which is common sense, there should be no need to standardise the gender.

Respectfully, Chris Gaunt, Calrec Audio Ltd.

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