Cardas Caps

I bought these because I have a brand new 5.5 and wanted to just protect the back from dust etc right out of the gate, not for sonics.

I just wanted to posted this let anyone considering buying these for sonics that they are essentially snake-oil-at least in my application. I noticed absolutely NO audible difference, nothing got quieter, or darker etc.

I recognize that every application is different, and that some might feel they need these to eliminate RFI etc...If so, I would suggest exploring other options, placing your resources where it has more effect.

In my experience, these have no benefit other than to protect from dust and corrosion. And quite honestly, they fit very loosely on my 5.5, so who knows.

Some tweaks are worth spending the money on, some aren't. This is one that IMO is not worth it.
I think a lot of this may be very dependent on the amount of RFI in your local environment. While I do not use the Cardas Caps, I do use shorting plugs, which are like RCA plugs where the hot and ground are soldered together, thus shorting the input (don't ever use these on an output). In the days of yore they were standard on Mac preamps and the like. In my environment, they absolutely make my preamp quieter, clearly and noticibly. Functionally, this is different from the Cardas product which simply covers the hot with the ground sheild.
Good to know...I would just suggest considering other, more effective, options if trying to resolve a rampant RFI problem-these aren't a complete solution, and made no difference in my system. Other than looking good, and protection, no sonic difference.
BTW, if you want to experiment, it costs practically nothing. You can buy RCA jacks from Radio Shack and solder the hot pin and sheild together. Since the plug is not carrying audio signal the quality is not much of an issue. For $1.79 you are in business. I also agree that this is not a panacea for severe RFI problems, which can be a bear. But, as part of a complete RFI abatement program, it helps. You may still need to relocate the component or power and audio cables, use ferrites all over the place, install dedicated lines and sheild your listening room in lead.
Viridian...Sounds like a better option quite honestly. Good points you make.