Do "Cardas Caps" make a difference?

A new inexpensive, and quite compelling, tweek are the caps George Cardas makes to cover unused input and output jacks, therefore rejecting stray EMF. This is a logical tweek, and I trust George's integrity here, but my question is: How noticeable is the improvement? Can everyone who has tried them hear a difference?
Hi FZXguy. This is one of the first tweaks I ever purchased, and have used them whenever an RCA jack needed covering. To be honest, I don't know what if any effect they have regarding EMF shielding, it's more a matter of peace of mind for me. However, I do like the idea of covering up something that is vulnerable to dust, corrosion and any household nasty that can make it's way into a small crevice.
Fzxguy, can't speak from personal experience but I had done a bit of research into these a while back and I did not find a single user who said it made a difference.

I agree and if you are truely happy with your system and are looking for that last tweak, this should be it. I am not moving pieces around anymore and have isolated all and just ordered my sets. BTW I think they are going up from $3 to $3.75 each. I heard an improvement using a Shakti stone but I want the piece of mind if I don't.
I have been using them for a little over a year and really didn't notice any sonic differences. It was just that "peace of mind" thing, they keep out dust and they look nice. There's even a signature version, or something like that.
I got a set in an auction and was able to cap unused RCAs on both my ARC CA-50 and my BAT VK-30SE (in another system), but was unable to hear any difference in either system. Like the other poster, I like the idea of neatening up my equipment and insuring against that stray RFI.
You will gain more ( on most systems ) by using / building "shunts" than by using "shields". The parts can be procured from Rat Shack and will set you back WAY less than what a set of the aforementioned "caps" cost.

The difference between shunts and shields are that shunts can only be used on unuesed inputs whereas shields can be used on any unused rca jack. As such, you can shunt the unused inputs and shield the unused outputs for maximum effectiveness. Sean
I have 90 of them installed. Couldn't hear any difference but I could swear my VCR's picture was less grainy after installing on the unused inputs. Testing with them on and off did produce a difference that only I could see. In other words, they probably do close to nothing. However, they look good (especially on front inputs) and they protect the RCA connector itself. Knowing what I know now I probably would have gotten plastic covers for protection only but I'm not dissappointed with the Cardas caps. Sean's idea is probably the way to go but I've heard many preamps don't like shorted inputs (I have no personal experience with that).
The Cardas caps were among a group of tweaks reviewed not long ago in "The Sensible Sound" (TSS). Now, I realize that TSS is not the ultimate high-end reviewer, but several of their writers have good systems, and like the rest of us, they have two ears and the ability to judge effects of tweaks on their system. The TSS article pretty much concluded that the Cardas caps added nothing (at best) and maybe even degraded the sound a bit.

Personally, I think that if you are concerned about dust getting into the inside of a component, then a plastic cap will work fine, and it's a whole lot cheaper than the Cardas gizmos. If your concern is about shunts vs. shields, then Sean has already given the best response above, and there is no need for me to comment further. (Good job, as always, Sean.)
You might notice that the Cardas ads claim that the caps help prevent RF noise from entering the system. They do NOT say that they eliminate RF noise. Nor do they claim to have any effect on the biggest sources of RF noise such as ground loops and cabling.
I own a systemful of Cardas cables, and think they are a good product and a good value. I have no experience with Cardas Caps, and don't intend on getting any. What I think these are is an absolutely genius idea from a marketing and profitability standpoint. They are the perfect answer to a question that nobody has ever needed to ask, and play brilliantly upon the famous neuroses of audiophiles. Here we have a product that - at least theoretically - makes logical sense, passes the "Couldn't Hurt" test, and looks and feels swell (and apparently can engender a little of the same feeling in their owners). They seem inexpensive when considered on a per-item basis, but I am sure that folks such as Leo above will testify that like playing a slot machine, this is one "cheap thrill" that can quickly get out of hand. My hat is off to George Cardas (or whoever's working for him) for coming up such an obvious-seeming idea - one which I'm sure has tweak-merchants everywhere smacking their foreheads and exclaiming, "Why didn't I think of that myself?!"
I had a slight buzz in my system. The Cardas caps helped lower the buzz volume by around 40%, so they did help. I resolved the buzz problem, but am happy to know the Cardas Caps do help in some circumstances. It's nice to know my expensive gear wont be gathering any dusty gook around the rca inputs anyway.
Zaikesman, I agree totally with your comments. That having been said, I own a set of them and when I reach behing my amp to change cables, my fingers love their cool reassuring metallic feel. My other favorite thing about them is that they came in a cute lil' plastic bag with a classy looking Cardas shell sticker on it :)
the cardas caps are well-made, cool looking and certainly do make a difference to george cardas' bottom line. BTW, an xlr/balanced version is now available to keep dust balls and other nasties from enterin' those three little holes. -cfb
Shunts don't necessarily have to be direct shorts. You can solder a resistor across a low grade RCA and achieve a "resistive shunt". This effectively "closes" that input without any adverse affects since it is not loading down the preamp circuitry. One would want to use the lowest resistance possible, but going as high as one or two hundred ohms should be fine for most any preamp / switchbox. After all, some sources have very low output impedances and hooking them up to the inputs typically does nothing "negative" to the system in itself.

For the record, shunts should lower your noise floor and could reduce / get rid of crosstalk between various inputs and sources. Try checking out these two threads that had similar subjects and info. Sean
Thanks for all your input!!
Is this what Sean is talking about? I have a YBA Integre DT amp in a small system in my home office. If the tuner is on I can hear the radio faintly as I go by an unused input when turning the input selector knob on the amp. If the CD player is also playing I can hear both (or just the CD player if the tuner is off). If I go by a used input where the component is plugged in and is not turned on, it is dead quiet. Therefore, when an RCA cable is plugged into that input, I do not get any sound if that unit is off, which is desireable. So a cap would do nothing, because it just covers the hole, but a shunt goes in the input and will cut-off the noise? A trip to Rat Shack is in order then! Thanks!
I have a dozen and I frankly can't tell if there's an improvement in sound. Oh, well, they look good enough and keep the dust out. I won't buy any more of them though.
I have 51 scattered throughout my main system. I also have some Cardas XLR caps. (The female XLR caps don't fit; I'm waiting for an upgrade.) I haven't heard any difference. I think its a good idea to keep dust and mosquitos out of the electronics. I also feel that improvements can be cumulative, i.e., multiple tweaks that are not individually audible can add up to an audible improvement. Perhaps these caps would fit in that category.
Yes. On my Audiomat Arpege they 'darken' the sonics to a point that I find quite objectionable. Proceed with caution!
I just installed a new pack of 12 on my KRC-HR and KSA-300S. I know when using my theater thruput because I have a long run of RCA's I used to have a slight low level buzz. Now there is nothing and the system seems even quieter. I only put them on my reference auidio (not video), and to me they can only help IMHO. Sean has great advice too, but I opted for these instead.
I made up shorted RCA's (guess these are shunts) for the unused inputs on my Radio Shack battery powered phono preamps (two used as dual mono's, thus unused inputs/outputs on each unit) and soldered 100 ohm resistors across RCA terminals and placed them on the unused output's of the preamps. The results: even quiter phono stages (these battery powered units were very quiet to begin with) and just better overall sound. As far as the Cardas Caps go, I have never tried them and instead used rounds of tin foil (on unused inputs) in the past. There was no difference in the sound, that I could hear, but I figured that they would help block dust (especially on my Musical Fidelity amp which is not a lot of fun to open up). I don't bother with them on "open" tube gear.