RCA Caps


Is anyone using RCA caps (plugs) on their unused audio connectors?

I'm considering going with either Telos or Cardas.

I like the idea of keeping dust out of these while benefitting from EFI/RFI rejection.
agiaccio
I have been using the Cardas for years. I wish I could afford them for the S-Video and all my XLR ins/outs that are unused, but as you have seen they are not cheap. For the SE caps there is a brans out there that has a little knob on them, if you can I would get those as the Cardas caps can be a pain to get off on SE jacks that are close.
I purchased the generic RCA Caps from Parts Express. I can't tell the difference between them or the Cardas ones visually. I've put them on varying pieces of equipment in my mostly mid-fi solid state systems and I haven't heard a difference either way with them in place. I've put them on preamps, CD players, integrateds even on a subwoofer amp and I could hear no difference. I agree with Theo to look at the caps with the little knobs on them. The generic caps I have can be hard to remove if your RCA jacks are in a tight space.
I bought a set of 10 pair of caps from Vintage Audio Lab off of eBay for about $20 shipped. Not really sure I can tell a difference, but better safe than sorry. Especially since it was only $20.
I bought 80 caps off eBay and they are pretty good for the price of 20 for $15 bucks.
I definitely noted a better screen on my Plasma TV with covering all the RCAs on the back. The background had less grain. So for the TV, they really are worth the money. For the stereo, i would say it too had a very slightly 'blacker' (quieter) background.
For the price of the Cardas, it is a little steep, but for some generic type, they are worth the bother, on stereo equipment, somewhat.
IMO, for unused rca INPUT jacks shorting plugs are preferable to caps, although of course in many cases I would not expect either one to make any difference.

Caps will do nothing to reduce coupling of internally generated rfi/emi onto the unused input lines, from where it might couple into the signal path that is in use. The same goes for rfi/emi that may originate externally, but which enters the component via a pathway that bypasses the rca jack and then couples onto those unused input lines. Shorting plugs can help in either of those situations.

Shorting plugs should not be used on output jacks, of course.

Regards,
-- Al
Excellent response as always Almarg, I was going to mention the same thing. I also, have not experienced a difference when using the RCA caps. I need to mention that I have never had a problem with EMI/RFI either and therefore YMMV.
I am gonna buy some clear plastic jobbys, anyone that does vintage knows that the jacks are closer together and with the plastic jobbys I can cut the edge off to fit. I just wanna keep the dust ( dead skin ) off.
I have tried RCA plugs off and on over the years, but I could never hear a difference.
A well-designed selector switch of a preamp will short all inputs except the one selected. With the old style rotary selector switch this requires an additional "deck". No doubt this deck has been eliminated to reduce cost.
IMO, for unused rca INPUT jacks shorting plugs are preferable to caps, although of course in many cases I would not expect either one to make any difference.
@almarg 

Is it even remotely possible that shorting plugs could cause some kind of "damage" (loosely and widely defined) to whatever audio equipment one would happen to install them on?
Hi Hal,

I can't envision a design in which a shorting plug applied to an RCA **input** would cause any problems.  Consider the fact that the essentially zero ohm impedance presented to the input by a shorting plug is not greatly different than the very low output impedances (e.g., 10 ohms or perhaps even less in some cases) of some components that might be used to drive that input.

Best regards,
-- Al
 
Al is correct, all you need is cheap $1 rca plugs that have been shorted, do get fooled into buying expensive caps that do nothing but may give you expectation bias.

Cheers George  
Thank you @almarg and @georgehifi
There is a small operation making and selling true RCA shorting plugs: Aurora Tronics in Sandy Hook, CT (phone number 203/426-9599). I bought some a couple of years ago, and they were cheap: $19.95 for 20 plugs. They also offer RCA phono cap covers (non-shorting, for outputs), at $7.95 for 20. They sent them to me with free shipping! Cardas' protective caps look nice, but do nothing, claims for providing shielding against RF and EMI notwithstanding.
@bdp24 

Thank you very much for that info. That pricing is good. Although you purchased them years ago and we know prices only head north as time marches on :)

I'll give them a call. In my case I only have phono inputs as I don't have an analog turntable. I would imagine if shorting plugs make any difference at all, shorting the phono inputs should make the greatest, so I'm intending to short those (as any other input).
I can’t envision a design in which a shorting plug applied to an RCA **input** would cause any problems. Consider the fact that the essentially zero ohm impedance presented to the input by a shorting plug is not greatly different than the very low output impedances (e.g., 10 ohms or perhaps even less in some cases) of some components that might be used to drive that input.

@almarg

Sorry to belabor this. I’m merely operating out an abundance of caution in this regard :)

I take your statement to *include* an LFE subwoofer RCA input as well as a phono input. Therefore, *any* type or kind of RCA input where audio is concerned would fall under the same umbrella where RCA shorting of input jacks are concerned.

And, I surmise the most benefit (if any benefit can be realized at all), would or should be from a phono input, which in the case of my amp has a phono input impedance of 47k Ohms, according to manufacturer spec.

EDIT: 
I also realize that operating out an abundance of caution might mean do nothing in this regard :)


Thanks for the follow-up, Hal, as it reminds me of one situation in which a shorting plug on an input could conceivably be harmful.

That would be on some power amplifiers which provide both XLR and RCA inputs, the intent being that only one of those inputs would be used. In some of those cases the signal pin of the RCA connector is wired directly to one of the two signal pins (usually pin 2) of the XLR connector. So if the XLR input is being used in those cases and a shorting plug is put on the RCA connector, the output circuit of the preamp or other component providing the balanced signal pair to the amp would have one of the two signals on its XLR **output** shorted to ground.

And I suppose a similar situation could conceivably arise in the case of some subwoofers, if both RCA and XLR input connectors are provided for a given signal type (i.e., for either an LFE input or an input that is intended to receive a full range signal).

And, yes, I agree with your statement about phono inputs.

Best regards,
-- Al

You're welcome @almarg  

And, thank you too!

I don't believe the RCA/XLR input scenario applies in my case. I'm using a Musical Fidelity M6si (which has phone RCA in) and Golden Ear Triton Reference (which has LFE RCA in).

I believe the scenario you are speaking of, where the RCA and XLR input is "shared" (i.e. one or the other) would be, for example, a Pass Labs INT-250. It's 1 and 2 inputs support RCA and XLR, however, it doesn't appear as though that unit wants both RCA and XLR connections in its 1 and/or 2 inputs simultaneously.
Yes, exactly, @gdhal . From the manual for the INT-250:
There are four inputs, two with XLR and RCA and two with RCA only. The XLR and RCA inputs on INPUT 1 (and INPUT 2) are connected so use XLR or RCA but not both. When using INPUT 1 & 2 with RCAs you should have the XLR shorting jumpers in place.
It’s unusual, though, for inputs of an integrated amp to be configured like that. Typically that situation arises with power amplifiers. But I suppose Nelson wanted to provide users with some added flexibility, by making it possible for those inputs to be used with either type of connection. While another designer might have simply made inputs 1 and 2 XLR only.

So with the INT-250 a shorting plug should not be put on the RCA connectors of inputs 1 and 2 if the corresponding XLR connector is being used.

Best regards,
-- Al

There is a small operation making and selling true RCA shorting plugs: Aurora Tronics in Sandy Hook, CT (phone number 203/426-9599). I bought some a couple of years ago, and they were cheap: $19.95 for 20 plugs. They also offer RCA phono cap covers (non-shorting, for outputs), at $7.95 for 20. They sent them to me with free shipping! Cardas’ protective caps look nice, but do nothing, claims for providing shielding against RF and EMI notwithstanding.

@bdp24

Appreciate that recommendation, but it appears to be a dead-end. The number is not valid, and the 860 version of CT area codes is a different organization. Googling for this outfit is also unsuccessful.

So, are there any other recommendations as to where to obtain caps and shorting plugs?
Search at eBay for "RCA shorting plugs" (without the quotes) and you'll find numerous sellers offering them, at low prices.

Best regards,
-- Al

Like the Cardas Caps they don't having to be shorting type caps to be effective. Cardas type caps are simple covers for unused input and output plugs. They should be placed over ALL input and output plugs for max benefit. Copper foil can be used in lieu of the real McCoy. 

I found the Aurora Tronics plugs in a 2015 ebay ad. It doesn't matter who makes them, as long as the hot center pin and outer ground are soldered together, to create the short. Anything less is merely cosmetic.
Sorry if this was covered earlier but why not just use caps to cover the unused plugs? I bought a set of 5 pairs gold plated caps for around $15. These are just "caps" with no pin inside.
Kalali, a shorting plug will have electrical effects, by lowering the input impedance of the unused input to essentially zero ohms. Low impedance circuit points are inherently less susceptible to pickup of electrical noise than high impedance circuit points, everything else being equal. Including pickup of noise that may even originate elsewhere within the same component, that may in turn find its way from the unused input path to the signal path that is being used, or to a circuit point (such as in the power supply) which can affect that signal path.

As was mentioned earlier, and despite some disagreement that was expressed, caps that do not short the input will do nothing other than perhaps reducing oxidation or corrosion of the ground shell that may occur over time, and keeping out a few dust particles.

Regards,
-- Al

https://www.ebay.com/p/8pcs-RCA-Cap-Protector-Dust-Proof-Brass-Gold-Plated-Shielding-Caps/1261404073...
That's what I using on my HT receiver unused inputs and remove the center pin for the unused outputs 
Like the Cardas Caps they don’t having to be shorting type caps to be effective.
These are good for nothing sound or noise wise.

Like Al said,
"a shorting plug will have electrical effects, by lowering the input impedance of the unused input to essentially zero ohms. Low impedance circuit points are inherently less susceptible to pickup of electrical noise than high impedance circuit points" " caps that do not short the input will do nothing other than perhaps reducing oxidation or corrosion of the ground shell that may occur over time, and keeping out a few dust particles."

Cheers George
Another solution is to chew a piece of gum along with shreds of aluminum foil and copper shavings. Once chewed, remove the metal reinforced gum and stick it on the unused RCA plugs. Done!
Georgie Boy, if I were you I'd seriously consider modifying your post to say, Cardas caps do nothing for the sound that I'm aware of. There, that's more like it!

🐩
wolf_garcia
Another solution is to chew a piece of gum along with shreds of aluminum foil and copper shavings. Once chewed, remove the metal reinforced gum and stick it on the unused RCA plugs. Done!

Yeah, but you have to be able to walk and chew gum simultaneously.

Useless....
I have had better results with Telos Gold RCA caps over Cardas. In A/B comparison, Telos caps further lowered the noise floor.  

May be I should try RCA shortening caps next....

Please note, I have taken great care of lowering noise floor and cleaning up AC signal in my dedicated room by deploying the Nordost QRT system. Our homes incoming AC aren't as quiet as we'd like to believe 😉
As long as you're going to put caps of some sort on your unused RCA inputs, might as well make them shorting caps. Why spend more for non-shorting Cardas' than for cheaper true-shorting caps? Seems obvious to me, a no-brainer if there ever was one!
No brainer. Good one! By the way, if memory serves putting Cardas caps on unused inputs/outputs on the TV and other non-audio components like the cable box helped the sound, too. I’ve got something similar. You know, keeps the dust out. 😬I know what you're thinking. "We want things that make good engineering and scientific sense." 😛

if memory serves
Gave yourself an out there sunshine.

Cardas caps on unused inputs/outputs on the TV and other non-audio components like the cable box helped the sound, too.
Bollocks!!! is this more voodoo from your leader/maker David Miscavige

Cheers george

What ever works. But I'll wager than if non-shorting caps are beneficial, shorting caps will be even more so. In this case, the "why" is no mystery.

Speaking of shorting caps and understanding them, here's a story Bill Johnson told at an instore appearance I attended in the 80's: ARC sent Harry Pearson their new SP-10 pre-amp for review, and shortly thereafter received a call from Pearson, who told Johnson there was something wrong with the pre. Bill, in an attempt to diagnose the problem over the phone, asked Harry some questions, and soon had his answer; Pearson had installed shorting plugs in the pre-amp's unused output RCA's. Well duh!

J. Gordon Holt evaluated the sound of components, be he also understood how they worked, having a technical electronic education. Pearson may have had a good ear, but was completely ignorant, technically. Having both is not a bad idea; it's a great b*llsh*t filter.

Good story, Eric (bdp24).  I took a quick look at the SP-10 schematic at arcdb.ws, and sure enough the design provides two pairs of main outputs, both of them RCAs, and on each channel the two RCA connectors are wired directly together!

Best regards,
-- Al
 
I would wager there some not so technical, that would put shorting plugs on an output, they’d remove it fairly quickly as there’d be very little to no sound from the other output, self healing (teaching) for those, and to only try them on inputs.

Cheers George
I had a long, love-hate relationship with the ARC SP-10 mk ii. I bought mine used, from somebody who had to have the new SP 11, and knowing what the SP 10 was capable of, I jumped on it. I had it sent back to ARC to have it gone over (at my cost) and have it retubed. I had a devil of a time finding quiet tubes, and I don't think it was the tubes that were causing the microphony, but how they were mounted. The unit went back and forth to ARC quite a few times; I bought new at the time gel type sockets (of a type similar to those used by Allnic) and ARC was willing to install them- they were also interested in the outcome. They didn't help. I had bags of 6dj8s that I would swap into the thing; I did have the factory at one point hot rod the unit to bypass more of the switches. It was a very good sounding preamp, with a sweet phono stage, but still of the old school ARC sound- not quite syrupy, but tending toward warm, rather than that more bleached sound of some of the later ARC stuff that sounded leaner. Once I got stopped using the Crosby Quad, which seemed to mask some of the low level noise of the preamp, and started using horn speakers of high efficiency, the preamp was simply too noisy to use. 
It was sort of my peak with ARC-- though I had several of their amps over the years (and still have my first one, a Dual 75a), I migrated away from ARC. Not due to any negative attitude on my part- I maintained a long cordial relationship with the parts department for decades.
When I got a Lamm L2 Reference line stage back in 2007 or so, I had SP-10 flashbacks- the unit was very similar in lay out, though the design and sound very far different. Classic old school preamp. 

How about little Santa hats for the holidays? Substitute tiny yarmulkes or turbans maybe…tiny football helmets or baseball hats! And geoffkait…don’t worry about walking and chewing as you can sit next to your rig (although a greasy iPhone may not need these things) to use my suggested gum remedy…have the orderlies help you after the exercise yard time...think of it as "arts and crafts."
I'm saturated in RF, for me the Cardas caps replaced tin foil and have reduced RF noise issues, but have not solved them entirely.
Gold Star for best quote of the week! ⭐️

"Not due to any negative attitude on my part- I maintained a long cordial relationship with the parts department for decades."



@geoffkait I saw what you quoted, so well put.
James, there is a real good chance that true shorting plugs will provide an improvement over the non-shorting Cardas caps. Do a search for them on ebay, where I found mine. I then sold my Cardas, as they were inferior to the far cheaper plugs. As a bonus, I got more for the Cardas caps than I paid for the plugs!
@geoffkait - I guess subtelty is not my strong suit :) Thanks for the award.
After my long time ownership and factory tweaking of the SP-10 preamp, my continued contact with ARC was mainly due to maintenance and refurbishment of my Dual 75a, which is now dormant again, but I bought a whole host of parts for it to be refurbished a few times, the last right before the company got sold. I used to deal with Leonard-- they were always pretty nice to me, and followed up.
@bdp24 Thanks for the pointer, I'll check out the shorting plugs...
whart, it's always a cause for concern when the original owner of a company sells it. Even more so when the owner was deeply involved in the design of his company's products, as was Bill Johnson in ARC's. I know some hardcore tube guys who feel ARC lost their way when they went hybrid (the SP-10 to the SP-11, in particular), and their products were more Rich Larsen's designs than Bill Johnson's. That an amp as old as the D75a, originally introduced in 1973 iirc, is still worth keeping running is a testament to the amp's design, that of Bill Johnson alone.
Just a follow up on my endeavors where RCA shorting plugs are concerned.....

I’ve obtained and installed these:

https://www.amazon.com/Viborg-Audio-Stopper-Plated-Protector/dp/B017DH76VS/ref=sr_1_1?ie=UTF8&qi...

I *cannot* detect a difference in the way my Musical Fidelity noise floor emanates the slightest "hiss" (no music source but volume cranked past 12) with or without the shorting plugs. So I’ll leave them on for "theoretical advantage".

I *can* detect a difference when I put them on the LFE input of my Golden Ear Triton Reference speakers. The otherwise (without caps) slight "wind tunnel breath of air) sound that is typical of speakers with internal amps does not seem to be present or if present has been lowered.

My assumption is that whatever benefit could be obtained by shorting inputs is the same regardless of whether or not the amp is class B or D, correct?

All good in any case :)

Happy New Year everyone!!
I use the Cardas on my Ayre.....absolutely no difference.   I suppose if you need them you do......