Is there a way to reduce cell phone interference in DIY KM-84?

[jp8]

So much of this is a bit over my head, but it is interesting how many different theories and suggestions there are in this thread among people who clearly have experience with this stuff, but few if any clear cut suggestions for part #s etc. Maybe that's reflective of the recalcitrant / intractable nature of the issue, but the absence of at least some agreed upon best practices seem conspicuously absent. I'm sorry you're having to wade through it all!

My interpretation of the many pieces of advice is slightly different from what you read: there is agreement on many of them, but many of them are also impractical or nearly impossible to implement inside OP's microphones. So until now, the best solution proved to be an external solution attached to the microphone.

But on some proposed solutions, there's indeed no agreement. Actually, this does not surprise me. In my 40 years of hardware design, I've learned the following:

• Even true or self-proclaimed EMC Gurus do not always agree.
• When you think you've done everything by the book, there could still be something you have overlooked. But the more experience and knowledge you gain, the less likelihood there is of a design flaw causing EMC issues. So there's always more to learn.
• Legacy designs (e.g. the design of the XLR plug) are often hard to improve because you cannot change it to an ideal design without introducing new issues. Designing for EMC should start from the very beginning of a project.

And it has been said before in this thread: it is difficult to solve such an issue if you do not know the complete picture. Ideally, you need the circuit diagram, BOM, PCB layout, and the actual hardware at hand that is having the interference issues. Now it feels like having to repair a broken car by phone. A car which stranded somewhere in Japan. And we don't know the model, we don't have the manuals, and we don't know which part between the front and rear bumpers actually broke down. Good luck with that... Then resolving the issue becomes a trial-and-error process. But even that is not uncommon for Gurus: we once hired an EMC expert for a certain issue, and it took him three days to fully map the circuit, including all the circuit parasitics, doing the math and simulations, and doing many measurements and trial-and-error experiments until he fully understood the root-cause and could prove his solutions worked.

Jan

 

[Cqwet Dbdfte]

As per usual, the math is applied after the experiment to confirm the often oversimplified math assumptions.
Helping our customers with only basic RF knowledge getting equipment to work to expectations often involves using your own eyes to find a problem invisible to the untrained eye.
It could be as simple as proper torque on a connector or assuming cables have no losses, or printed specs on parts are actually correct.

 

[ricardo]

But I found the order in which bead and caps were place somewhat confusing. Maybe I'm missing something, but in order to work as an LC filter for RF sigals entering from the cable, I would have expected the caps to sit on the PCB. I see that also being done in other mics, e.g. Gefell MT71S comes to mind. In the Schoeps circuit the beads and caps would act as an LC filter for outgoing RF signals.

It's NOT a 'filter'. It's to prevent RF currents flowing around inside da Faraday cage. If the caps were on the PCB, RF would flow through the inductors and then go through the caps to the PCB, then to p1 and the earth tag .... before it got to the Faraday cage. Depending on the construction of the inductor, this might give MORE RF floating around inside.

With the caps on the pins, RF will flow through the caps to the Faraday cage by the shortest possible route and avoid the 'high' Z of the inductors.

Ferrite beads are better than good inductors cos they need to be lossy for the signals going out of the mike else there will be a peak in the response.

The best place for the caps is OUTSIDE da Faraday cage .. which is how da Neutrik connectors are done. dai h.'s pic of a recent Schoeps actually shows where they would have WANTED to put the caps

When designing the output filter circuit of the Calric mics, did you also consider the LC circuit as used in a.o. the Gefell M295?

Of course and tried it out too. That's why I was amused much later when I found Dip Ing Wuttke had used exactly the same arrangement. Maybe there's a Schoeps CB Radio too

 

[ricardo]

In https://groups.io/g/MicBuilders/files/Ricardo/LNPrimer I talk about the Input Loop. You have to join.

This is the loop aerial at the input of all LN circuits. If this is large, you WILL have serious problems with noise & RFI. This is so important that I will often use smaller caps sacrificing some LF performance to get physically smaller caps with shorter leads. in that critical loop.

 

[Cqwet Dbdfte]

It's NOT a 'filter'. It's to prevent RF currents flowing around inside da Faraday cage. If the caps were on the PCB, RF would flow through the inductors and then go through the caps to the PCB, then to p1 and the earth tag .... before it got to the Faraday cage. Depending on the construction of the inductor, this might give MORE RF floating around inside.

With the caps on the pins, RF will flow through the caps to the Faraday cage by the shortest possible route and avoid the 'high' Z of the inductors.

Ferrite beads are better than good inductors cos they need to be lossy for the signals going out of the mike else there will be a peak in the response.

The best place for the caps is OUTSIDE da Faraday cage .. which is how da Neutrik connectors are done. dai h.'s pic of a recent Schoeps actually shows where they would have WANTED to put the caps

Of course and tried it out too. That's why I was amused much later when I found Dip Ing Wuttke had used exactly the same arrangement. Maybe there's a Schoeps CB Radio too

Correct, the first element should be cap, but a cap input LC filter is still an LC filter. Feed-thru capacitors are commonly sold as "filters" and may also include inductors.
No filter is perfect getting 30dB - 40dB rejection is good for a simple filter. More sections are needed if that is not enough.

Having a "leaky" coax cable does not help anything, so a system approach helps. The XLR connector is showing its age in this context.

 

[jp8]

It's NOT a 'filter'. It's to prevent RF currents flowing around inside da Faraday cage. If the caps were on the PCB, RF would flow through the inductors and then go through the caps to the PCB, then to p1 and the earth tag .... before it got to the Faraday cage. Depending on the construction of the inductor, this might give MORE RF floating around inside.

With the caps on the pins, RF will flow through the caps to the Faraday cage by the shortest possible route and avoid the 'high' Z of the inductors.

Ferrite beads are better than good inductors cos they need to be lossy for the signals going out of the mike else there will be a peak in the response.

The best place for the caps is OUTSIDE da Faraday cage .. which is how da Neutrik connectors are done. dai h.'s pic of a recent Schoeps actually shows where they would have WANTED to put the caps

Of course and tried it out too. That's why I was amused much later when I found Dip Ing Wuttke had used exactly the same arrangement. Maybe there's a Schoeps CB Radio too

Thanks for clarifying. Understand your reasoning and how the ferrites work. Yet, I would still call it a filter. Just not the 2nd order LC filter I mentioned. Anything that keeps unwanted signals outside your circuit, either by blocking, diverting the signal, or absorbing it, I would qualify as a filter. Just different topologies with different modes of action. But enough about that.

I agree with you that ferrites should be used instead of inductors. But why not use a single bead between pin 1 and the circuit ground? That should have a similar effect and saves one ferrite bead. I use this method too, just as Neutrik in their EMC plug and Takstar do in their CM-63. Maybe it would work even better: if the ferrites do not have exactly the same impedance, the CM RF signals would convert into Normal Mode signals and the AM demodulation in both BJT outputs would generate different demodulated LF signals. If the demodulated signals were of the same polarity and level, they would be rejected by the CMR of the mic preamp, at least when assuming a good preamp.

Talking about the Neutrik EMC plug: You said the best place for "the caps" is outside the Faraday cage. Agree on that. But "the caps" on the XLR inside the mic are on the XLR from pin 2 and pin 3 to chassis ground / pin 1, shorting RF to the reference. In the Neutrik EMC plug, they are placed circumferentially between the cable shield and connector shell. So the effect on reducing RF sensitivity may be the same, the mode of action is different. This arrangement has minimal inductance and closes the interruption of the cable shield and mic tube Faraday cage by the XLR. In this way, it minimizes the CM RF signals appearing on the mic XLR terminals. See the picture below from Neutrik, explaining how the plug works and a simplified circuit diagram.

Jan

 

[jp8]

@joulupukki: I don't know if you feel like experimenting any further, now that you've made a significant improvement with the Neutrik EMC plug, but I have another idea to try. It is not THE solution to your RF interference issue, but it might help. FYI: I have built my SMT version of the KM84 for the CM-60 and have done some experiments on it to improve RFI susceptibility.

As there was little room between the transformer and XLR plug, I was not able to place the ground ferrite bead I referred to in earlier posts on the switch side of the transformer. I knew that this place would be far from ideal, but I thought: let's just give it a try. And it was far from ideal: if I replaced the bead with a zero Ohm jumper resistor, the RFI remained unchanged. What DID help was putting a bead in series with C4 (coupling cap to transformer) and as close as possible to the JFET. Testing with my RF jammer, the results were as follows:

• Stock CM-60 = Ref.
• KM-84 circuit, without bead: 7 dB worse compared to Ref.
• KM-84 circuit with bead: 5 dB better compared to Ref. So a 12 dB improvement over the KM-84 circuit without bead.

The bead I used was Murata type BLM11HA601SG which I had lying around, but which is now obsolete. In future experiments, I will use Murata BLM18HD102SH1, which has a high impedance in the cell phone frequency range. Sorry, but it's an 0603 size SMT part...

At 2nd thought, I think I can make the cutout for the transformer smaller and add some filter parts near the XLR, where they are supposed to be. In the next revision, I will include this filter. I hope I can finish the PCB update before my holidays and order it, so I can test the updated version later in April.

To be continued...

Jan

 

[joulupukki]

@joulupukki: I don't know if you feel like experimenting any further, now that you've made a significant improvement with the Neutrik EMC plug, but I have another idea to try. It is not THE solution to your RF interference issue, but it might help. FYI: I have built my SMT version of the KM84 for the CM-60 and have done some experiments on it to improve RFI susceptibility.

As there was little room between the transformer and XLR plug, I was not able to place the ground ferrite bead I referred to in earlier posts on the switch side of the transformer. I knew that this place would be far from ideal, but I thought: let's just give it a try. And it was far from ideal: if I replaced the bead with a zero Ohm jumper resistor, the RFI remained unchanged. What DID help was putting a bead in series with C4 (coupling cap to transformer) and as close as possible to the JFET. Testing with my RF jammer, the results were as follows:

• Stock CM-60 = Ref.
• KM-84 circuit, without bead: 7 dB worse compared to Ref.
• KM-84 circuit with bead: 5 dB better compared to Ref. So a 12 dB improvement over the KM-84 circuit without bead.

The bead I used was Murata type BLM11HA601SG which I had lying around, but which is now obsolete. In future experiments, I will use Murata BLM18HD102SH1, which has a high impedance in the cell phone frequency range. Sorry, but it's an 0603 size SMT part...

At 2nd thought, I think I can make the cutout for the transformer smaller and add some filter parts near the XLR, where they are supposed to be. In the next revision, I will include this filter. I hope I can finish the PCB update before my holidays and order it, so I can test the updated version later in April.

To be continued...

Jan
View attachment 124805

Very interesting. Yes, I'd still like to improve the RF rejection in my DIY mics without having to rely on the Neutrik EMC plugs.

I'm assuming the pad switch worked? Cool!

Also, I don't see the JFET or the bead in your picture, but maybe they're on the other side?

Too bad I didn't read this 'til now. I ordered a couple of ferrite beads (with an order of parts for a U87 build) from Mouser this morning. But, it looks like their impedance values are below 100 at 100Mhz. :-|

https://www.mouser.com/ProductDetail/710-74270001
https://www.mouser.com/ProductDetail/710-74270010

I was thinking of trying one of these around the gate of the JFET, close the the JFET body.

My thinking was, if this doesn't improve things, I will likely just build a new PCB that's closer to the style of the layout of the MP build and go from there. Or...twist your arm in sharing your gerber files.

Good luck with the continued improvements! I like the progress you're getting.

 

[MicMaven]

No- the capacitance between the foil hat with your hair as an insulator and your body itself will then create a capaictor turning the whole thing into an antenna - so no hats.

Not so, Dick Tracy - because it would then be ... um ... (I cannot resist a bad pun) ... a CAPACITY HAT! James

 

[MicMaven]

Understand your reasoning and how the ferrites work. Yet, I would still call it a filter.

Why not call it a "choke?"

why not use a single bead between pin 1 and the circuit ground? That should have a similar effect and saves one ferrite bead.

I believe multiple beads are cumulative in effect. Winding the lead through the bead as like a toroid often has a multiplying effect.

N'est ce pas? James

 

[MicMaven]

I'd still like to improve the RF rejection in my DIY mics without having to rely on the Neutrik EMC plugs.

Good day, Mr. Joulupukki.

After re-reading the entire thread, I have pose a few questions and observations, which may be way off base as I am still a rookie at some of this ... but here goes anyway:

* Why not ground Pin 1 at the mixer end of the cable, connecting it to mixer chassis? I believe you connected Pin 1 to the XLR shell at the mic end, but not at the mixer and (I believe) not at BOTH ends of the cable. I have solved similar RF issues in amateur radio mic cables by connecting Pin 1 and shell (and, ipso facto, with the transceiver chassis.) While this may not be the most recommended practice, it has solved similar problems, and, to coin a phrase, I favor "experience over form."

* Speaking of ferrite beads, perhaps you could take a cue from the amateur radio playbook by installing one or more clamp-on ferrite beads on your microphone cable, forming a simple RF choke. I am encouraged you can tame the problem by modifying the cable using the Neutrik EMC connectors. You get more bang for your buck if you can loop the cable through the toroid multiple times. Looping the cable through a single toroid provides substantially more choking impedance than adding a second bead. You might consider FairRite Mix 31 for HF frequencies, Mix 43 for UHF, and possibly Mix 61 or 63 for UHF frequencies. Search for articles on this type of choke and Pin 1 problems by Jim Brown, K8YC, on the Internet - he has several articles that measure the choking effect of various configurations and mix types, especially in connection with microphones and audio gear.

* Wild Alex Guess No. 20838 - Occasionally, a LONGER wire works as well as a shorter wire when a lead is acting as an antenna. Perhaps slightly longer twisted wires inside the mic body would get the click. Doing this solved a problem with my underground sprinkler system when 40 meter QRO transmissions activated just one of the sprinkler heads. Adding wire decoupled the system at the problematic frequency. Occasionally, it is merely a matter of avoiding resonance (including avoiding harmonic frequencies) and a longer wire may work as well as a shorter one to decouple the offending device. Sounds silly, but I believe experience triumphs over theory.

* I am unsure whether you determined whether the problem is limited to your particular cell phone, or or is endemic to the entire species. If limited to your phone, the solution may entail modifying the phone instead of the mic. (Of course I am reaching a bit on this aspect, but there is no harm asking ... I hope.)

* How did you determine the capsule, itself, is not the problem? Does the problem occur with the original capsule? Does it occur with the original board? I apologize if I missed previous mention hereof.

* For what it is worth, I second the motion to upgrade the cable to one with better shielding, especially in conjunction with the Neutrik EMC connectors and/or add-on ferrite beads.

Just a few observations and serving suggestions from one who has solved similar RF interference issues in similar situations. / James

 

[Cqwet Dbdfte]

@joulupukki: I don't know if you feel like experimenting any further, now that you've made a significant improvement with the Neutrik EMC plug, but I have another idea to try. It is not THE solution to your RF interference issue, but it might help. FYI: I have built my SMT version of the KM84 for the CM-60 and have done some experiments on it to improve RFI susceptibility.

As there was little room between the transformer and XLR plug, I was not able to place the ground ferrite bead I referred to in earlier posts on the switch side of the transformer. I knew that this place would be far from ideal, but I thought: let's just give it a try. And it was far from ideal: if I replaced the bead with a zero Ohm jumper resistor, the RFI remained unchanged. What DID help was putting a bead in series with C4 (coupling cap to transformer) and as close as possible to the JFET. Testing with my RF jammer, the results were as follows:

• Stock CM-60 = Ref.
• KM-84 circuit, without bead: 7 dB worse compared to Ref.
• KM-84 circuit with bead: 5 dB better compared to Ref. So a 12 dB improvement over the KM-84 circuit without bead.

The bead I used was Murata type BLM11HA601SG which I had lying around, but which is now obsolete. In future experiments, I will use Murata BLM18HD102SH1, which has a high impedance in the cell phone frequency range. Sorry, but it's an 0603 size SMT part...

At 2nd thought, I think I can make the cutout for the transformer smaller and add some filter parts near the XLR, where they are supposed to be. In the next revision, I will include this filter. I hope I can finish the PCB update before my holidays and order it, so I can test the updated version later in April.

To be continued...

Jan
View attachment 124805

Twist those transformer wire pairs, cancel/attenuate stray magnetic fields.
A better shielded cable type may be the first choice IF the rest of the mike is well shielded.

 

[jp8]

Very interesting. Yes, I'd still like to improve the RF rejection in my DIY mics without having to rely on the Neutrik EMC plugs.

I'm assuming the pad switch worked? Cool!

Well, it's not actually a pad switch but a low-cut switch. To be honest, I have not tested it yet. I have to spend some time tuning the cut-off frequency to my taste. Its cut-off frequency depends on the input impedance of the mixer and the amount of feedback around the JFET. Or simply put, it depends on the value of C2. I don't have the time right now.


"Also, I don't see the JFET or the bead in your picture, but maybe they're on the other side?"
Yes, indeed. All SMT parts are on the bottom side. Sorry for the poor quality picture. My camera on my phone is of abysmal quality.




"Too bad I didn't read this 'til now. I ordered a couple of ferrite beads (with an order of parts for a U87 build) from Mouser this morning. But, it looks like their impedance values are below 100 at 100Mhz. :-|

https://www.mouser.com/ProductDetail/710-74270001
https://www.mouser.com/ProductDetail/710-74270010

I was thinking of trying one of these around the gate of the JFET, close the the JFET body."

Cell phone frequencies are 600 MHz and up, where the beads you chose still have a rising impedance with frequency. I think they could work. Maybe even put a bead on all pins, if space allows?

"My thinking was, if this doesn't improve things, I will likely just build a new PCB that's closer to the style of the layout of the MP build and go from there. Or...twist your arm in sharing your gerber files. "

I'll PM you about this, if you don't mind. My idea was to offer the PCBs through PCBWay when I'm satisfied with the performance.

"Good luck with the continued improvements! I like the progress you're getting."

Thanks! The results so far and the ideas I still have are indeed motivating me to improve the design further.

Jan

 

[jp8]

Why not call it a "choke?"

I didn't call it a choke because I was referring to its function, rather than the physical properties or the part type

I believe multiple beads are cumulative in effect. Winding the lead through the bead as like a toroid often has a multiplying effect.

N'est ce pas? James

Oui et non... Windings through a bead have a shunt capacitance, which creates a resonance frequency. Above the resonance frequency, effectiveness declines. I don't know what kind of ferrites or chokes Ricardo used in his design, though. Those piggy-nose type ferrites you are referring to which have 1 or more windings are often quite big and less suitable for use in an SDC, I would think.

The RF current through the two ferrite beads in the output configuration Ricardo proposed, will return to the XLR shield through pin 1. So a single impedance in the ground pin should work equally well, is my assumption. But those nasty RF currents are always flowing in your circuit at places where you'd least expect it, so maybe some of the RF current will flow through the small capacitance of the mic tube to mother earth, back to the transmitter, which is also capacitively coupled to earth ground. In that case, it would be best to have ferrites and/or Common Mode chokes in all three XLR wires. This is what Takstar does in their CM-63: a Common Mode choke plus two ferrites in the signal lines and a ferrite bead between signal ground and pin 1.

Jan

 

[jp8]

Good day, Mr. Joulupukki.

After re-reading the entire thread, I have pose a few questions and observations, which may be way off base as I am still a rookie at some of this ... but here goes anyway:

* Why not ground Pin 1 at the mixer end of the cable, connecting it to mixer chassis? I believe you connected Pin 1 to the XLR shell at the mic end, but not at the mixer and (I believe) not at BOTH ends of the cable. I have solved similar RF issues in amateur radio mic cables by connecting Pin 1 and shell (and, ipso facto, with the transceiver chassis.) While this may not be the most recommended practice, it has solved similar problems, and, to coin a phrase, I favor "experience over form."

* Speaking of ferrite beads, perhaps you could take a cue from the amateur radio playbook by installing one or more clamp-on ferrite beads on your microphone cable, forming a simple RF choke. I am encouraged you can tame the problem by modifying the cable using the Neutrik EMC connectors. You get more bang for your buck if you can loop the cable through the toroid multiple times. Looping the cable through a single toroid provides substantially more choking impedance than adding a second bead. You might consider FairRite Mix 31 for HF frequencies, Mix 43 for UHF, and possibly Mix 61 or 63 for UHF frequencies. Search for articles on this type of choke and Pin 1 problems by Jim Brown, K8YC, on the Internet - he has several articles that measure the choking effect of various configurations and mix types, especially in connection with microphones and audio gear.

* Wild Alex Guess No. 20838 - Occasionally, a LONGER wire works as well as a shorter wire when a lead is acting as an antenna. Perhaps slightly longer twisted wires inside the mic body would get the click. Doing this solved a problem with my underground sprinkler system when 40 meter QRO transmissions activated just one of the sprinkler heads. Adding wire decoupled the system at the problematic frequency. Occasionally, it is merely a matter of avoiding resonance (including avoiding harmonic frequencies) and a longer wire may work as well as a shorter one to decouple the offending device. Sounds silly, but I believe experience triumphs over theory.

* I am unsure whether you determined whether the problem is limited to your particular cell phone, or or is endemic to the entire species. If limited to your phone, the solution may entail modifying the phone instead of the mic. (Of course I am reaching a bit on this aspect, but there is no harm asking ... I hope.)

* How did you determine the capsule, itself, is not the problem? Does the problem occur with the original capsule? Does it occur with the original board? I apologize if I missed previous mention hereof.

* For what it is worth, I second the motion to upgrade the cable to one with better shielding, especially in conjunction with the Neutrik EMC connectors and/or add-on ferrite beads.

Just a few observations and serving suggestions from one who has solved similar RF interference issues in similar situations. / James

OK, you addressed this to Mr. Joulupukki, but I hope you don't mind. I will reply to some of your observations.

About connecting the XLR shield to chassis and/or signal ground: maybe I missed it, but I cannot remember it could be interrupted at either side of the cable. This is basically impossible with condenser microphones. The mic cable shield doubles as a ground return for the phantom power. No connection means no sound from the mic. A complete overview of good and bad practices of connecting mic cables can be found in this famous article from Rane here.

You're suggesting to "tune" the wires (Which ones, btw? There are only wires to the transformer), but I highly doubt whether that will have any significant effect. Like others already mentioned: once you have the RF garbage inside your mic tube, it will always find a path to your victim, the JFET. The RFI must be kept outside by blocking it at the front door (XLR plug) or as close as possible to the victim, the JFET. This was one of the major lessons learned at the EMC trainings I followed: if you have a filter somewhere in your signal line, make sure the RFI carrying conductor does not "see" the secondary side of the filter, or else the RFI will simply bypass the filter. I think I've proven that with the ferrite bead on my PCB on the wrong side of the transformer.

Jan

 

[jp8]

Twist those transformer wire pairs, cancel/attenuate stray magnetic fields.
A better shielded cable type may be the first choice IF the rest of the mike is well shielded.

Twisting could help if there are normal mode currents flowing through the wires. But I would expect the RF currents to be common mode. OP already tried twisting the transformer wires, btw. Without noticeable effect.

Jan

 

[MicMaven]

I hope you don't mind. I will reply to some of your observations.

A complete overview of good and bad practices of connecting mic cables can be found in this famous article from Rane here.

RIGHT - I have read that article many times - good stuff.

The RANE article states the following, which explains why I suggested tying ground to equipment chassis - at both equipment and microphone ends of the cable:

The method specified by AES48 is to use balanced lines and tie the cable shield to the metal chassis (right where it enters the chassis) at both ends of the cable.​

Moreover, I have encountered real world cases where tying Pin 1 to chassis (i.e. XLR shell) at both ends was necessary to eliminate EMI/RFI in the mic input. Also, I have several condenser microphone cables which have Pin 1 tied to the XLR shell (chassis ground) at both ends, and they all work well.

Am I missing your point?​

[PS - I appreciate the direct reply - no worries here - I am here to learn.] // James //

 

[MicMaven]

I didn't call it a choke because I was referring to its function, rather than the physical properties or the part type ...

I apologize - I do not understand your proffered distinction.

The objective is suppressing RFI in the audio chain. A toroidal choke is (often) a doughnut-shaped, wire-wound passive electronic component used to suppress electromagnetic interference in various devices. Clamp-on ferrite beads can also be used. I design and build antennas for amateur radio. While remaining a rookie, I was once named a member of the "design team" of a commercial German antenna manufacturer and a couple of my ideas have become part of commercial products!

We often employ clamp on and circular ferrite beads, and wire-wound toroid transformers (baluns, un-uns) including 1:1 toroid windings as an RF "CHOKE" to suppress RFI. ​

I do not understand how the OP's case is materially different, requiring a different name. I am NOT being obstreperous or picky. This a bona fide term of art, not a casual moniker I made up. These devices are an RF Choke, even when constructed solely of coiled transmission line. (Which almost, but not quite, suggests another way to minimize RFI in the subject case.)

Again, I am NOT just being picky. I posed a serious question and, while I appreciate your reply, I do not understand the purported distinction. James

 

[ccaudle]

The RANE article states the following, which explains why I suggested tying ground to equipment chassis - at both equipment and microphone ends of the cable:

The method specified by AES48 is to use balanced lines and tie the cable shield to the metal chassis (right where it enters the chassis) at both ends of the cable.​

Note that AES48 and AES54-1 call for making the connection in the equipment connector, not the cable. That is not really a big distinction in small setups, but in large installations (think arenas, multi-room conference centers, etc.) if the shield is tied to the cable connector shell it introduces a path for multiple connections to building power ground wherever the cable touches building metal, or has to go through a patch bay which is mounted on building metal.
Some people have noted that cables with shield tied to connector shell will occasionally pick up hum when a person holds the connector. I have not noticed that personally, but it may depend on the mic output impedance or other internal wiring details.

I only point that out for completeness, this is one of those cases where it probably makes sense to do whatever works best for your situation, as long as you do it with your eyes open and realize that there could be cases where that performs worse, and that if you buy off the shelf cables they will likely be wired to the standard without a pin 1 to shell connection, and if you want that you would have to modify the commercial cables.

 

[dai h.]

re: Neutrik EMC connectors:

(I tried to upload these before but they didn't show up in the preview, but I guess they were okay? Anyway, this is my attempt at explaining (to myself) how the connectors worked. Caveat: I am not any kind of expert whatsoever (just a hobbyist) so I have no problem deleting these (or maybe amending them) if my attempted explanation is incorrect.)