That's actually kind of a funny story. We actually DID use locking female RCA jacks...the same ones that most companies use. But once they arrive, we modified them by cutting the chassis ground leg off of them and pull the locking mechanism out of them...a process that takes a lot of man hours to do.
The reason why we do this though may surprise you. First, the chassis ground path on the metal-faced versions is pretty easy to understand why it was undesirable to use stock. Linking your signal ground right to the chassis as it's bathing in neighboring component's RF fields isn't what you'd want. Having a short ground path there is nice for passing some tests, but terrible for the sound.
The locking pin was another matter entirely. Space is typically not an issue for us...since we're designing the components, we can make them about any size we want and high end Audio isn't about having 75 inputs, just making the fewer inputs a lot better. The issue is that these mechanisms are made pretty much 100% steel with a nickel plating that is all magnetic. The Ayre gear is sensitive enough that it picks up ferrous materials near the signal path, creating a significant negative sound impact. We first discovered this when using ferrite beads...they'd sound great at first, making us want to use more and more, but learned that after a few months/years in the system, really trashed the sound until you replaced them or, better yet, just removed them to avoid knowing that the sound is slowly degrading constantly.
They (Gary Mulder, our current domestic Sales Manager and Charley) later experimented with ferrous materials near the XLR lines and could hear the sound change significantly (for the worse) when such metals were near the signal path. That led to other tests what showed the same in-circuit. For this reason, we're really neurotic about avoiding such materials. All of our wire connectors are custom-made with materials that are non-ferrous, our capacitors and resistors are also custom-made for Ayre to avoid steel and nickel. This means that the components we use have to be hand-made instead of automated in their construction and we're always having to stay ahead on lead times, etc. since they're never stocked parts...nobody else that our vendors use request such parts. We then have the components further treated in other ways that aren't really relevant here that we've found improve the sound. Every screw is stainless or brass, the chassis is aluminum, and even the brackets are stainless steel. Of course stainless is slightly magnetic, but vastly better than steel, nickel, etc. Ultimately, the only real magnetic piece left is the transformer, which there's little we can do about that!
It's a ton of work and expense to deal with, but it's a very small part of what makes the Ayre products sound like they do. I don't mind sharing little secrets like this, as for most companies the amount of work for the payoff would seem insane to go through, so I doubt many are going to use this. I hope that explains in a very long way why we don't use such mechanisms. Also, we've never experienced an XLR connector just spontaneously getting loose without a cable end needing to get replaced anyway...if they can just fall out without being touched, you're going to want to replace the female cable end. Leaving it alone and relying on the mechanism to hold it in place just means that you're likely not getting much of an airtight connection between the surfaces, leading to oxidation over time of the mating surfaces and degrading sound over time. This can happen when you're unplugging or plugging in regularly. You really want a tight connection to minimize the amount of air getting between the surfaces.
Hope that helps!
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