Speaker Selector Switchbox changes audio quality?

[radardoug]

To the arrogant know-it-alls that use the term "audiophools" - stop it. If you have not researched this issue then you aren't in any way qualified to pass judgement. Reminder: scientific method requires peer review. Otherwise it's very poor signal to noise ratio. At the end there's a screenshot showing what I'm talking about.

I have built switch and relay boxes for this purpose have never heard one that doesn't f-k up the sound in some way. Less is more. You have to have really good signals, amps and speakers to make it worthwhile, though. Even the wire can lose audio quality. I'd get rid of them. They're ok for the consumer grade convenience but you'll be much better off directly wiring the spkrs to the amps. You want to be professional, don't hinder yourself with inferior gear. It was clear to me that A-B boxes aren't good unless it's really well designed. It wasn't worth the effort to continue to use them.

Several things:

1. From the looks of the box these are double pole, double throw power switches. It's OK but switches that have a center off will isolate both speakers and amplifiers such that they can't be connected together, i.e. amp to amp or spkr to spkr.

2. Yes, switch contacts can degrade audio quality. It may be subtle but they will. If you are switching amps and speakers while playing there may be arcing on the internal switch contacts which will definitely degrade the connection. Speaker relays are subject to the same problems. Any thing between the amp output and the speaker can and probably will degrade the signal. Look at the screen shot.

3. Over time those switch contacts will oxidize unless they are fully gold plated and sealed, but they can still arc. Oxidation degrades the contacts and forms diode like connections that partially rectify the signal. If you flip the switch and each time the sound quality changes at all either oxidation or arcing could have occurred, even with self - wiping contacts.

4. My suggestion is to replace the toggle switches with DPDT center off gold plated types. Expensive, yes but much more reliable if you want to keep this box. You may have to find rotary switches. Also rate them for at least 20 amps. Better yet, wire up your best amp to the best speakers with your best wire and forget the box.

Here's a screenshot of audio trying to pass thru degraded contacts in speaker fuse holders. Note that in the lower trace there is diode rectification that drops in and out. Small signals will be affected most. I took this shot during routine amp testing.

Diode rectification is a one-way street.

The fact that you suggest gold plated switches for a speaker controller indicates that yes you are right, there are lots of fools out there! Gold plated switches are not the best choice for this. Gold plated switches are generally for low current applications. And of course, if you dont keep your gear in good condition, then you will have problems.

 

[ccaudle]

Gold plated switches are generally for low current applications

It might take come careful reading of datasheets to find a switch which can handle high currents, but also will pass low voltage signals cleanly right away. Switches often have a minimum voltage rating, which I have heard typically indicates that the plating might develop some thin oxidation layer which is reversed with current flow, but requires a minimum voltage to get that current flowing. Probably more of an issue when switching low level signals (e.g. mic level) than speaker level.
NKK has some issue on that consideration here:
https://www.nkkswitches.com.hk/engineering/electrical.html(these sentences below are just the beginnings of the relevant paragraphs, not the complete text)

"Gold plated contacts are recommended for dry circuits, which are defined as very low energy. In circuits where the voltage is below 28 volts DC and current is below 100 milliamps (dry circuits), no arc develops as the contacts open or close....."

"Silver contacts are recommended for electrical levels above 0.4VA. Although silver tarnishes, it is a good conductor and this electrical energy is sufficient to break through the tarnish to give reliable performance...."

"...The gold over silver contact material provides a reliable, tarnish free, contact surface for logic level switching. When this same contact material switch is used in power level circuit, the gold plating is removed by contact arcing. If an attempt is then made to use this same switch in a logic level circuit (where no arcing occurs). The low current condition cannot provide adequate contact wiping or cleaning."

 

[k brown]

Bought one of these recently on eBay (there's one on there now) - I remembered it from my teen years.

Very high quality. Enameled steel enclosure, nice sized screw terminals, big robust switch inside, with a smooth, solid feel.

 

[Mr. Moscode]

yup, you can blow up tube amps with simple speaker switches. There was even a warning about that in the Amazon product write up.

JR

I wasted time re-reading this thread to find the cited insult (I didn't find it).

Over the decades I have wrestled with many audiophools but don't recall addressing individuals with that specific pejorative. I have used it in general when the shoe fits on sundry topics.
===
Regarding switch contacts degrading audio, yes faulty jacks and faulty switch contacts can be audible. Replace any faulty components.

In the course of doing my old day job we used plenty of A/B tests but I never used listening tests for primary design, mainly to confirm that I measured and optimized the correct design factors.

JR

Disco Volante posted Sunday 1/7 at 11:27 AME "As for the speaker switch, you are switching high currents, so a big switch will be "better" than a small one. Whether anyone will be able to hear it is another question. I know that the audiophools shun such switches (it would sort of void any point in buying $1000+ cables, if there was any in the first place)."

I didn't address Mr. Volante directly. I addressed the use of the term, which I find derogatory. This argument between meter readers and listeners is all over this forum, John.

 

[Mr. Moscode]

The fact that you suggest gold plated switches for a speaker controller indicates that yes you are right, there are lots of fools out there! Gold plated switches are not the best choice for this. Gold plated switches are generally for low current applications. And of course, if you dont keep your gear in good condition, then you will have problems.

Don't switch the speakers while playing music, especially loud! Use simple common sense care for your switch, which is between your audio source and speaker all the time. I assume everyone here is interested in quality in their work. Don't damage your tools!

Only thing to watch for is residual DC from a solid state amp which could cause mild arcing. And if that is there the amp needs to be fixed. Tube amps always need a minimal load on the output to dampen flyback action of OPT which can arc an output tube and smoke a few resistors or even arc the transformer.

AS for logic level switches being relegated only to logic level circuits, that's narrow thinking. There's a lot of audio below .4 volts. You need the switch to work perfectly linearly throughout the entire dynamic range. We're not switching a motor connected to the mains on and off where there is plenty of power available to override switch wear. Switching a highly inductive loads at full power like that requires a contactor rather than a toggle switch. But I don't recommend a contactor as it doubles the number of contacts in series with the speakers.

The whole premise of this thread is how speaker switches affect audio quality. I posted from my experience from 40 years of working in high end audio with 12+ successful products under my belt. Products for audiophiles, those who want the most pleasing audio quality, which is generally better than commercial sound reinforcement products.

The best switch is NO switch. Less stuff is MORE audio.

I contributed to this conversation to address the concerns of the OP because I have first hand experience and knowledge of this very issue, which is the point of the forum. I don't engage in topics I have no interest in or knowledge about. If I'm wrong, I'll admit it. I learn a lot here.

I've made my point about the pejorative use of the word "audiophool". I take offense at it and if so moved I'll continue to point out the insult wherever I find it. If your recordings sound bad on a quality hi end system, you have more work to be done.

 

[Newmarket]

Better yet, wire up your best amp to the best speakers with your best wire and forget the box.

Kind of missing the point that this is often done in a studio environment to deliberately compare on different speaker types - Soffit Monitors / Mid and Near field monitors / "consumer level" etc. Not just to get the best sounding result.

wrt "Don't switch the speakers while playing music, especially loud! Use simple common sense care for your switch, which is between your audio source and speaker all the time."
Can't disagree with that - DO NOT switch when there's audio present. Avoids the major hazards.

Also consider - whilst there are small signal / large signal considerations as to the contact type and materials - it's not unusual for an amplifier's "Anti-Thump" circuitry to be implemented with chunky relays in the signal path.

 

[JohnRoberts]

Disco Volante posted Sunday 1/7 at 11:27 AME "As for the speaker switch, you are switching high currents, so a big switch will be "better" than a small one. Whether anyone will be able to hear it is another question. I know that the audiophools shun such switches (it would sort of void any point in buying $1000+ cables, if there was any in the first place)."

He makes an interesting point. I have engaged in the "Meter Reader vs. Golden Ear" debate since the 1980s. In my old "Audio Mythology" magazine column in RE/P magazine I dedicated one column back then to speaker wire (short version, it's the wire resistance). Funny (hifi) speaker wire is a ripe category for separating fools from their money.

A decade or two ago, I revisited this speaker wire topic on a professional sound reinforcement forum when a respected member claimed that he could definitely hear a dramatic improvement from using XYZ premium speaker cable. I did not dismiss him as a Phool, but dug a little deeper into his personal speaker/wire experience. Long story short it turned out that his premium speaker wire was higher resistance than typical speaker zip cord. This significant wire resistance for the length he used, was forming a variable voltage divider with the loudspeaker's changing impedance over frequency (due to a passive crossover). The variable attenuation result from this changing voltage divider was a modest (major fraction of dB) HF boost over the top octave. He heard that frequency response difference and because the funny speaker wire was more expensive, he was biased to ASSume that it was the more accurate reproduction. After I opened his eyes to what was actually going on he stopped advocating for premium speaker wire.

I didn't address Mr. Volante directly. I addressed the use of the term, which I find derogatory. This argument between meter readers and listeners is all over this forum, John.

In my decades of experience designing and merchandising audio SKUs I have encountered numerous examples of misguided subjective conclusions. Don't get me started on phono preamp magazine reviews.
===
We have forum rules requiring civil discourse in forum exchanges (rule #4). Since you have announced your sensitivity to that particular term I trust nobody will call you that. These civility rules apply to person to person exchanges. Vague derogation of third parties is not covered (otherwise we could never discuss politics).

On topic, over the decades I have encountered any number of Audio_____ who claimed that they could hear a single switch contact in their audio path. Even a casual inspection of a basic recording console audio circuitry reveals multiple switch contacts in the primary audio path. My response back then stands today. "If you can hear a switch contact, it is faulty and needs to be replaced."

JR

PS: Subjective audio perception has been well studied over the decades. AES journal published some well respected papers back last century.

 

[Mr. Moscode]

Kind of missing the point that this is often done in a studio environment to deliberately compare on different speaker types - Soffit Monitors / Mid and Near field monitors / "consumer level" etc. Not just to get the best sounding result.

wrt "Don't switch the speakers while playing music, especially loud! Use simple common sense care for your switch, which is between your audio source and speaker all the time."
Can't disagree with that - DO NOT switch when there's audio present. Avoids the major hazards.

Also consider - whilst there are small signal / large signal considerations as to the contact type and materials - it's not unusual for an amplifier's "Anti-Thump" circuitry to be implemented with chunky relays in the signal path.

I get the studio issues. I had one in NYC for about 20 years. It has to sound good on everything- big monitors and 4"Auratones (awful tones). I'd burn a disc and listen to it in the car, at home, on a boom box etc.

As an amplifier designer and repairman I can tell you there are at least 2 ways to mute the amplifier during turn on. In my amplifier, using tubes to drive a mosfet follower output stage, a timed mute relay shorts the drive signal and input to ground for about 40 seconds and is out of the signal path when operating.

In my Luxman receiver there is a multi-pole chunky relay in series with the output that disconnects the speakers during turn on stabilization, about 10 seconds. I had to replace that when I overhauled the receiver. It's pleasant sounding and does a very good job but does not convey the low-level detail that my amp does.

Every connection has its consequences. Less is more.

 

[Mr. Moscode]

He makes an interesting point. I have engaged in the "Meter Reader vs. Golden Ear" debate since the 1980s. In my old "Audio Mythology" magazine column in RE/P magazine I dedicated one column back then to speaker wire (short version, it's the wire resistance). Funny (hifi) speaker wire is a ripe category for separating fools from their money.

A decade or two ago, I revisited this speaker wire topic on a professional sound reinforcement forum when a respected member claimed that he could definitely hear a dramatic improvement from using XYZ premium speaker cable. I did not dismiss him as a Phool, but dug a little deeper into his personal speaker/wire experience. Long story short it turned out that his premium speaker wire was higher resistance than typical speaker zip cord. This significant wire resistance for the length he used, was forming a variable voltage divider with the loudspeaker's changing impedance over frequency (due to a passive crossover). The variable attenuation result from this changing voltage divider was a modest (major fraction of dB) HF boost over the top octave. He heard that frequency response difference and because the funny speaker wire was more expensive, he was biased to ASSume that it was the more accurate reproduction. After I opened his eyes to what was actually going on he stopped advocating for premium speaker wire.

In my decades of experience designing and merchandising audio SKUs I have encountered numerous examples of misguided subjective conclusions. Don't get me started on phono preamp magazine reviews.
===
We have forum rules requiring civil discourse in forum exchanges (rule #4). Since you have announced your sensitivity to that particular term I trust nobody will call you that. These civility rules apply to person to person exchanges. Vague derogation of third parties is not covered (otherwise we could never discuss politics).

On topic, over the decades I have encountered any number of Audio_____ who claimed that they could hear a single switch contact in their audio path. Even a casual inspection of a basic recording console audio circuitry reveals multiple switch contacts in the primary audio path. My response back then stands today. "If you can hear a switch contact, it is faulty and needs to be replaced."

JR

PS: Subjective audio perception has been well studied over the decades. AES journal published some well respected papers back last century.

Well studied but no concrete conclusions. Too many variables. Thus a subjective term like "audiophools" has no evidence to support its use as a blanket term. I take offense because my audience members are mostly audiophiles. So by associating with them as my target audience some members on this forum will consider me an "audiophool". I would say the audiophile manufacturer looks beyond the accepted norms of studio work and gear, where money is at stake, to find what differences everything in a product negatively affects and spends time trying to find a way around them.

Pro sound and audiophile products have 2 differing priorities. Pro sound has to work every time and provide adequate performance because money (lots of it) is at stake. Audiophile sound has to provide superior performance as the primary objective. Fussy equipment, although not desirable, can be tolerated if it performs and gives the deep connection to the music most of the time. Audiophiles are also like hobby motorcycle riders. Some want to ride different bikes out of curiosity as part of the hobby, others find a comfortable reliable bike and keep it going for decades.

I started to go on but I'll call it at that. Great to have this forum, though.

 

[radardoug]

One of the problems with the Internet in general is that anybody can express an opinion, and often this results in inaccurate information. A lot of people who are less knowledgable will read this information. There are many on this forum with a great deal of knowledge which they impart regularly, and this is good. But bad information is not good. This was the reason I posted after Mr Moscode posted that gold plated switches were the way to go. They are not. This is misinformation. Please think about what you post, and whether it stands the test of accuracy. The one thing Mr Moscode has said that I agree with, is less is better. If you dont need a switcher box, then dont use one. And John's point on speaker cables is so true. I once had a case in a theatre where the system amplifiers were at least 150 metres from the speakers. I demonstrated to the management that the subs sounded completely different when the amplifier was at the speaker vs 150 metres away. And the difference was not subtle.

 

[JohnRoberts]

Well studied but no concrete conclusions. Too many variables.

Concrete conclusions about subjective human audition require controlled listening tests that have statically significant results. These are incredibly difficult and time consuming to perform effectively.

Over my decades long career I have had to deal with numerous flawed (uncontrolled) listening tests. The worst I recall was one time when I was out of town and my boss had an impromptu uncontrolled listening comparison performed between our product and a competitor. .

Thus a subjective term like "audiophools" has no evidence to support its use as a blanket term.

I can only share what that nomenclature means to me. "Audiophiles" are enthusiasts of high fidelity sound reproduction and generally customers for premium Hifi SKUs. "Audiophools" are indeed a pejorative appellation, a little word play conflating fools and philes. Generally referring to people who make unfounded conclusions based on subjective listening.

I take offense because my audience members are mostly audiophiles. So by associating with them as my target audience some members on this forum will consider me an "audiophool". I would say the audiophile manufacturer looks beyond the accepted norms of studio work and gear, where money is at stake, to find what differences everything in a product negatively affects and spends time trying to find a way around them.

?

Pro sound and audiophile products have 2 differing priorities. Pro sound has to work every time and provide adequate performance because money (lots of it) is at stake.

Professional Install fixed sound (like background music for stores or factories) demand even higher up-time than live sound reinforcement that mainly demands that the show must go on. One service call in the fixed sound industry can completely wipe out the profit from an installation job. Professional studio gear pursues very high performance, but sometimes gets distracted by exotic concerns (gold plated this or that).

Audiophile sound has to provide superior performance as the primary objective. Fussy equipment, although not desirable, can be tolerated if it performs and gives the deep connection to the music most of the time. Audiophiles are also like hobby motorcycle riders. Some want to ride different bikes out of curiosity as part of the hobby, others find a comfortable reliable bike and keep it going for decades.

When I drove a motorcycle I was interested in acceleration. I owned an old 2 stroke yamaha street bike that sounded like an outboard motor but pulled like a mule.

I started to go on but I'll call it at that. Great to have this forum, though.

Yes, it is a good forum to exchange ideas as long as we remain civil in our disagreements.

JR

 

[Mr. Moscode]

his was the reason I posted after Mr Moscode posted that gold plated switches were the way to go. They are not. This is misinformation. Please think about what you post, and whether it stands the test of accuracy.

I'm sure you will have no problem explaining why I'm a purveyor of misinformation. Got evidence?
I'm open to your explanation.

 

[Tubetec]

We used sell those speaker switch boxes in the hi-fi shop to the odd customer who wanted backround noise in another part of the house , typically the box would be run off the B speaker selector on the reciever ,
Inside it is a bank of resistors in series with the outputs , it dumps appreciable power in the resistors to maintain a reasonable load on the amp with multiple speakers , definately not something you want in the signal path to your favourite speakers .
We used qualify the sale to customers by saying we dont consider these boxes hi-fi equipment ,only for backround music .

 

[Mr. Moscode]

Concrete conclusions about subjective human audition require controlled listening tests that have statically significant results. These are incredibly difficult and time consuming to perform effectively.

Do gentlemen prefer Hanes? Do blondes have more fun? Chocolate or Vanilla?

Over my decades long career I have had to deal with numerous flawed (uncontrolled) listening tests. The worst I recall was one time when I was out of town and my boss had an impromptu uncontrolled listening comparison performed between our product and a competitor. .

Audio wars! Gentlemen pick your weapons. Been there, done that.

I can only share what that nomenclature means to me. "Audiophiles" are enthusiasts of high fidelity sound reproduction and generally customers for premium Hifi SKUs. "Audiophools" are indeed a pejorative appellation, a little word play conflating fools and philes.

You are correct sir. I don't see how it could be meant as anything else. That audiophiles aren't many on this forum doesn't justify it's use. It's still a pejorative. We don't accept the n-word. Or do we?

Generally referring to people who make unfounded conclusions based on subjective listening.

By who's standard? Who is anyone on this forum to say? To sit in judgement because one can plot a load line, knows ohm's law, spends one's life in a studio or with a soldering iron makes them no more an expert about hi end Hi Fi than it makes them an expert MLB batting coach, or musician. They're a fool to think they have the license to mock the people who buy the products of their work. How many bands were recorded with Peavy amps on stage? how many indie CD's have been made in a bedroom? The arrogance is astounding. it's a professional pitfall.

People make unfounded conclusions about everything! As long as we can call ourselves a democracy with the 1st amendment intact the public is free to misinform the public about anything. Clorox for covid, moon landing is a hoax, . . . . .
George Costanza: It's not a lie if you believe it.

Besides it's their audiophile hobby money! Is anyone on this forum poorer because audiophiles exist? I'm richer because audiophiles exist because my customers overwhelmingly enjoyed my products. they just want something better than a Macy's rack system. 2,500 amps and preamps of mine have made a lot of people happy.

Do gentlemen prefer Hanes? (very old commercial for stockings reference.)

Professional Install fixed sound (like background music for stores or factories) demand even higher up-time than live sound reinforcement that mainly demands that the show must go on. One service call in the fixed sound industry can completely wipe out the profit from an installation job. Professional studio gear pursues very high performance, but sometimes gets distracted by exotic concerns (gold plated this or that).

Experiments to improve your sound aren't a distraction unless you've given up. If you can justify the investment in time and money then have at it. Research is science. I've still never seen a gold plated plug or jack get shaky, rusty or deteriorate.

When I drove a motorcycle I was interested in acceleration. I owned an old 2 stroke yamaha street bike that sounded like an outboard motor but pulled like a mule.

Great. I liked riding just for the sheer enjoyment of riding on a motor and 2 wheels. Something very primal about it. Then I got a Goldwing, for a comfortable thrill, then covid came causing me to reevaluate my relationship with death, then the Goldwings went away. I still have the jackets. Great in this cold weather.

Yes, it is a good forum to exchange ideas as long as we remain civil in our disagreements.

JR

Indeed.
GK

 

[JohnRoberts]

Do gentlemen prefer Hanes? Do blondes have more fun? Chocolate or Vanilla?

As a 15 year employee working for Peavey, I am more than a little aware of the power of branding and market perception

Audio wars! Gentlemen pick your weapons. Been there, done that.

I thought that was over back in the 80s...

You are correct sir. I don't see how it could be meant as anything else. That audiophiles aren't many on this forum doesn't justify it's use. It's still a pejorative. We don't accept the n-word. Or do we?

that is surely a hyperbolic stretch and as far as I can tell nobody has called you a phool.

By who's standard? Who is anyone on this forum to say? To sit in judgement because one can plot a load line, knows ohm's law, spends one's life in a studio or with a soldering iron makes them no more an expert about hi end Hi Fi than it makes them an expert MLB batting coach, or musician. They're a fool to think they have the license to mock the people who buy the products of their work. How many bands were recorded with Peavy amps on stage? how many indie CD's have been made in a bedroom? The arrogance is astounding. it's a professional pitfall.

It's spelled Peavey... I have a personal rule to not argue with people on the internet about what they claim to hear.

People make unfounded conclusions about everything! As long as we can call ourselves a democracy with the 1st amendment intact the public is free to misinform the public about anything. Clorox for covid, moon landing is a hoax, . . . . .
George Costanza: It's not a lie if you believe it.

methinks you doth protest too much.

Besides it's their audiophile hobby money! Is anyone on this forum poorer because audiophiles exist? I'm richer because audiophiles exist because my customers overwhelmingly enjoyed my products. they just want something better than a Macy's rack system. 2,500 amps and preamps of mine have made a lot of people happy.

you are conflating the enmity toward audiophools as an attack on all audiophiles, it is not.

Do gentlemen prefer Hanes? (very old commercial for stockings reference.)

Experiments to improve your sound aren't a distraction unless you've given up. If you can justify the investment in time and money then have at it. Research is science. I've still never seen a gold plated plug or jack get shaky, rusty or deteriorate.

Speaking of gold, I put gold plated RCA jacks on my last phono preamp to end all phono preamps. Not because I believed they would sound different, but because I expected customers to believe that they would make a difference.

Great. I liked riding just for the sheer enjoyment of riding on a motor and 2 wheels. Something very primal about it. Then I got a Goldwing, for a comfortable thrill, then covid came causing me to reevaluate my relationship with death, then the Goldwings went away. I still have the jackets. Great in this cold weather.

I liked the raw acceleration but had to be careful to make sure I was pointed in the right direction when I twisted the throttle hard. One time I was passing a car and gave it a little too much throttle. The front wheel does not steer when lifted several inches off the ground, so I was headed toward the oncoming traffic, until I released the throttle to drop the front wheel and regain steering control.

Indeed.
GK

I had one resident golden ear working inside Peavey. He worked in the transducer group and I used him on several speaker related projects. He was a good balance of a competent electrical engineer and serious audiophile (he has published at least one technical paper in the AES journal related to multi-tone IMD). We would have our share of how many angels fit on a pinhead, friendly audio poop discussions.

One time my golden ear friend asked me to approve an engineering change order as a favor because his actual boss (engineering director) refused to approve the $0.25 cost increase to replace a passive crossover capacitor with a better film cap. His boss was worried about upper management seeing him approve a cost increase. I was willing to take a little heat to use the better component where it could actually make a difference. Of course that heat never came.

JR

 

[Newmarket]

you are conflating the enmity toward audiophools as an attack on all audiophiles, it is not.

+1

 

[k brown]

My understanding of gold plated jacks/plugs is that for gear that doesn't always have cables connected to jacks that are only occasionally used, gold jacks won't become problematically oxidized during the time that nothing is connected to them, and thus protecting them; so that when they are used, they'll make clean contact.

For system inputs that always have cables connected, the plugs will protect the jacks from oxidation, thus gold offers no advantage.

For inputs that are very frequently connected/disconnected, the soft gold plating will wear away very quickly.

 

[Newmarket]

For system inputs that always have cables connected, the plugs will protect the jacks from oxidation, thus gold offers no advantage.

For inputs that are very frequently connected/disconnected, the soft gold plating will wear away very quickly.

In general, connectors (and particularly audio and general types) do not guarantee a gas tight connection. This means that protection against oxidisation may be a problem.
Yes, gold is a soft metal and not ideally suited to frequent mechanical wear through plugging/unplugging.
Interestingly, afaik (I'm not a metallurgist) silver contacts are interesting in that silver oxide - while looking a bit rough - remains highly conductive ?

 

[k brown]

In general, connectors (and particularly audio and general types) do not guarantee a gas tight connection. This means that protection against oxidisation may be a problem.
Yes, gold is a soft metal and not ideally suited to frequent mechanical wear through plugging/unplugging.
Interestingly, afaik (I'm not a metallurgist) silver contacts are interesting in that silver oxide - while looking a bit rough - remains highly conductive ?

Yes, I was careful not to say prevent oxidation, but might have been better to say 'will slow' oxidation.

I think it's only BNC that claim to be gas-tight.

 

[Newmarket]

I see. My take on that is that in general each re-insertion will result in different points of cold welding. See your point though. Also need to consider the "springiness" of connections esp eg TRS jack sockets.
I'm not aware of that claim for BNC. Wouldn't that also apply to eg TNC ; F-Type and similar coax and triax connectors ?