Noise blocking caps

Has anyone tried noise blocking caps on the DS DAC and/or transport? Cardas, Audioquest, etc sell caps for XLR, RCA, HDMI ports that purport to block RFI/EMI interference. I’m sure they do a great job of keeping dust out, but has anyone noticed an actual improvement in the noise floor from using these products?

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I’ve used the Telos Audio. I think they actually do reduce noise a bit in the DSD. There is one instance where I am certain they DID reduce noise: using with my NuWave Phono Converter. In place they just eradicated a barely audible hum I had from that nothing else did. I don’t believe Telos Audio makes them any longer.

I once owned the Luxman L-509x integrated amp and currently have their P-750u headphone amp. I kept the Luxman-supplied caps on all L-509x unused ports. Thankfully, I did not notice any audible noise on that dead-silent amp. However, since the original owner did not supply the caps that came with the P-750u headphone amp, I queried Luxman regarding purchase of them. This was the response I received:

Those plastic caps are supplied at the factory to protect the gold plated connectors and XLR’s during overseas shipments and handling. That is their only purpose.

We do not sell these plastic caps separately. And the Luxman engineers at the factory do not recommend keeping any of them in place during use of any Luxman device.

The plastic can retain small electrostatic charges that can negatively affect sound quality if kept in place. Please continue to enjoy your P-750u as is, without compromising the sound.

Regards, JP

John Pravel, VP Sales
LUXMAN America, Inc.
27 Kent Street, Suite 105A
Ballston Spa, New York 12020
Office: 518-261-6464
Mobile: 518-522-1494

Not sure if the XLR and RCA caps provided on Luxman equipment function the same as the blocking caps mentioned above. I hope they would have been designed to prevent buildup of electrostatic charge. But I am passing this info along FYI. Might be of special interest to those who currently own Luxman equiment and still keep their protective caps on the unused ports.

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Just to be clear - do you mean “caps” as lids, or capacitors built into a plug?

I was thinking caps as lids. There are also shorting plugs to short the inputs.

Has anyone tried shorting straps on the XLR input on the DAC?

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Here is an example of the Cardas RCA caps. No experience with them, so no recommendation.

Cardas RCA Caps

You cannot use the Cardas caps on the Directstream dac if they short the output as the rca out connects to the transformer and would affect the output of the balanced connectors.

Good to know, as I have not used them, and as such can’t recommend their use. Not having a DSD DAC comes into it as well… :thinking:

Cardas RCA Caps

From the image they don’t appear to offer shorting capability, just a cap over the RCA. They appear to be cosmetic IMO.
Personally I wouldn’t bother.

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That’s an interesting response from Luxman especially given the challenge of getting the dealer who sold me my P-750u to provide me with the XLR and RCA caps. Like you, I thought that they kept out the dust and had no impact on the SQ.
How are you finding your 750u? I found it to be a quantal improvement cubed on the built in headphone jack on the BHK PreAMP.
Have you tried XLR balanced cables on your headphones with the 750? I have Sennheiser HD800s and the balanced cables vary between $25 on Amazon, $400 or so from Sennheiser - when they have them in stock - into the thousands. I’d appreciate any insights/experiences you might have on this topic.

Indeed, cosmetic only. Dusty desert dweller here; I have my unused RCAs (on all electronics) covered with uxcell silicone caps, about $10 for 20 at Amazon.

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The caps don’t short the input. They’re just caps, but the metal composition is supposed to block rfi/emi interference.

To short an input, you’d need shorting plugs like these. They’re only for inputs, not outputs.

For some reason, RCA caps are relatively inexpensive while XLR caps are quite pricey. I’m wondering if a shorting strap on the XLR input on the DS DAC would be a good alternative. At least, would it not do any harm?

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Ive used them for years. Never really noticed much of a difference.

I put them in the peace of mind catergory. They are very well made. Only contunue to use them beacuse I still have them around.



I’ve always liked the Luxman presentation due its tone, wide soundstage, smooth detail retrieval and how it never beomes congested even during massive orchestra crescendos that someone like Wagner might dish out. BUT the synergy with the interconnects plays a major role in this. Like most card-carrying audiphiles I have gone through a virtual library of ICs over the years. I finally stopped when I purchased Purist Audio Design Aqueous Aureus rca and xlr cables. They provide the detail and tone I like without that sharp-edged decay that loud high treble notes sometimes exhibit, as for example with a ffff piccolo passage, But they also sound good to me on rock, pop, electronic, etc. with great speed and impact while keeping the bass alive for an enjoyble, viceral listen. They mate perfectly with the Luxman. And are equally satisfying with my Pass and Mac amps.

I recently purchased Acoustic Zen Silver Reference II xlr cables to try with the Luxman. No dice. A bit too incisive for my tastes. But wow! What a great synergy with my Mac MHA200. Clarity, drive, impact, tone, bass and sweet high end. What a transformation from the PAD cables I was using with the MAC. For classical the Mac/AZ SRII don’t quite beat the Luxman with PAD cables, but for most other music genres they are equal to the Luxman, but with their own characteristic presentation. With rock and other high impact recordings (like Sousa marches) they are my go-to combo.

One final comment. Even if you could hear my setup in my system it may not cut the mustard for you. My hearing and mental processing of nerve signals may be quite different from yours. So Mike you will just have to continue to throw those IC darts until you hit upon a combination with your Sennheisers that’s your cup of tea. Hopefully that will come sooner rather than later and the cashed saved can be used for other “must have” audio toys.

P.S. This hearing/brain processing thing is a pet peeve of mine when reading equipment reviews. While I might agree with a statistical probabilty-based performance conclusion (presented as a normal distribution curve) from a significant population of listeners listening to the exact same system in the exact same location, a single reviewer’s opinion is not worth much to me other than it providing info about the component. And of course, the former is not possible. At the very least ALL professional reviewers should have a standard hearing test performed and a graph of frequency versus dB level of their hearing thresholds published with every review (or in a reader-accessible link). Many well regarded reviewers are not spring chickens and their hearing may very well be attenuated to varying degrees. I know mine ain’t what it used to be. Then I could at least compare their hearing ability curve against mine and perhaps value their subjective comments about the components they review. Assuming they are not influenced in any manner by the manufacturer of the component under review. Ahemmmmmm.

I have those shorting straps on my krell amp, because I’m using the RCA inputs. I bought them from moon audio.

Big fan of Luxman here as well, having a 509X, simplicity in one box and the sound is as you describe it. I have been satisfied with Iconoclast SPTPC I purchased from a forum member. I had Purist Colossus a long time ago. They are now long gone, good wire and smooth operators IME.

“So Mike you will just have to continue to throw those IC darts until you hit upon a combination with your Sennheisers that’s your cup of tea”.
Thanks for the detailed feedback that I’ll bear in mind as I experiment with ICs for the 750. I’m limited to RCAs as I use the XLR on the D10 X for my preamp. The 750 u is very sensitive to nuances in IC SQ, I found AQ better than MIT S3.
I was also hoping you’d share any experiences you may have had with Balanced XLR Headphone cables.

Which pins do you short on your Krell? The 1 and 3 pins? Or the 2 and 3 pins?

Here’s a picture of the shorting pin location on my krell KSA 300s amplifier

Tried. Not once. Twice and thrice.

Maybe in lesser equipment it works well … but horses for courses.

The noise blockers worked well with my VTL The Ultimate but with my Doge 8 Clarity, they destroyed the SQ.

A dimunition in SQ in my Esoteric K-03xd and the M1200s.

I’ve given these up on my big rig. I’ll try it on my low-fi study rig, maybe.