I've been "ackified", round 2

[marty]

I started a new thread on this subject because I think the general relevance of RFI and EMI shielding is broader than the issue as it pertains only to ack’s system thread.

To bring readers up to date, recall that Tasos did some remarkably easy and inexpensive work to shield his MIT network boxes from spurious EMI and RFI that he felt was highly beneficial to his system. See post 481

http://www.whatsbestforum.com/showthread.php?2740-ack-s-system-end-of-round-1/page49

Following Tasos’ lead, I then explored some easy mu metal and copper foil shielding to virtually eliminate the hum caused by my industrial 24v power supply for my Goldmund Studio turntable. See post 503

http://www.whatsbestforum.com/showthread.php?2740-ack-s-system-end-of-round-1/page51

Tasos also led the way with some more superb detective work by demonstrating that shielding his DAC power provided a noticeable improvement in performance. See post 504

http://www.whatsbestforum.com/showthread.php?2740-ack-s-system-end-of-round-1/page51

With these observations as an obvious roadmap that even Detective Clouseau could follow, it seemed obvious to me to try some mu metal/copperfoil shielding on my MIT SHD interconnect network boxes that connect my Meitner DX2 to my VTL 7.5 III preamp . So I undertook a pretty easy and cheap arts and crafts project and constructed some mu metal/copper foil-lined boxes to snugly fit around my MIT network boxes.



The results were enormously beneficial and pleasing. Tasos’ previous descriptors included phrases such as “ sounded so incredibly life-like and even more dynamic (micro and macro)” and “metallic nature of cymbals out of this DAC right at this moment is something I have not yet heard anywhere else, as is the distinct duration of long-running notes within a complex music passage (not just a trailing note at the end of a track). Just food for thought on how noise can mask the music; it would be an understatement to say I am re-discovering my entire music collection.”

I thoroughly concur. The singular phrase I would use to characterize the resultant changes sonically is a decrease in top end grunge most likely due to spurious EMI/RFI noise suppression that renders the music more life-like and sonically pleasing.

Well, now it looks like I’m on a mission. Where else in my system could some easily available shielding provide improved benefit? Even better, it seems that there are some readily available tools that could take a good deal of guesswork out of the pursuit. These are portable EMI/FRI meters and sweeping one’s system might be a good way to find the sources of radiation that might be sonically beneficial if shielded appropriately. Stay tuned.

As an aside, I think the recent comments by Gianluigi and others on the Italian Kuros AC power cable that uses mu metal shielding intrigue me. I was privileged to hear Gianluigi’s system last June and was mightily impressed with that AC cable, not only because of the mu-metal shielding, but also because it used Furutech FI-11 Copper terminations that I currently favor. The question that interests me is how much of what I heard might be due to the benefit of the mu metal shielding in the Kuros cable, as opposed to the other components of that cable (i.e. wire, terminations etc.)? I obviously don't know the answer to that question, but that doesn’t detract from the subject of the thread, which is that I believe EMI/RFI shielding is something deserving of further exploration in our quest for better sound. Even better, there are apparently inexpensive solutions to this potential problem if it exists in your system.

 

[LL21]

Awesome news! Thanks for that. In my own less technology-savvy way, i have used Entreq wraps (nearly 2 dozen) across the power cables as my primary source of shielding and have found incredibly positive results that match both of your descriptions. I [think] Entreq Receivus is supposed to do something similar in terms of EMI/RFI...again more of the same in particular with cymbals and extreme frequency being as if not more extended...but far more resolved with stronger more distinct and natural tonality.

I look forward to reading more about this...and perhaps will revisit this after my most recent focus on some mechanical isolation on the Tripoint which is currently a lot of fun as the various iterations have now settled on my current one.

Where did you find the most benefit so far in your various 'EMI/RFI upgrades'? And where will you explore next?

 

[ack]

Marty, this is really great! Impressive work! One thing, don't forget to route the copper shield to a ground, and thin wire will do.

Yes, the RFI/EMI issue is a huge subject and we are just scratching the surface. I think part of the problem you and I are experiencing - and now solving - may have to do with the unfiltered nature of the Spectral designs, and their intrinsically wide bandwidth. Another thing to try is mumetal around the phono RCA plugs, which I've been doing for years, and in fact, it's an easy A/B to confirm: put mumetal on just one channel and turn up the volume.

My XP-25's main unit is also wrapped in mumetal/copper for years now, and I don't want to belabor the point that what comes out of the factory is not exactly top notch execution, unlike say Moon or other properly constructed phono stages. And all power cable plugs around the phono are also wrapped in mumetal, because there is no shield inside them. The net effect is that this phono has no hum, and if I were to compare with what came out of the factories (Pass, MIT), I'd say it's easily -30dB quieter, and I am quite serious about that, to the point that I now love this modified XP-25!

I hope others will also share their RFI teaks here, and thanks for starting this thread...

 

[ack]

I wanted to direct the audience here to the wikipedia page on mumetal https://en.wikipedia.org/wiki/Mu-metal and show to what extent one can take this, like shield connectors, cables, even your entire audio system. Examples from that page:

Five-layer mu-metal box. Each layer is about 5 mm thick. It reduces the effect of the Earth's magnetic field inside by a factor of 1500.


Mu-metal shields for cathode ray tubes (CRTs) used in oscilloscopes, from a 1945 electronics magazine


Mu-metal submarine cable construction

For example, it would not be weird to build shielded tunnels for our cables, and sufficiently away from them in order not to materially affect capacitance, but it would look ugly. Let's see how wild can our imagination go...

 

[marty]

4 quick comments:

1) In the lab, faraday cages are often not grounded. I don't think its mandatory to ground one's mu metal/copper foil boxes but it is certainly easy to do so. In my case, it was easy enough to try, but I did not notice any obvious benefits one way or the other. Individual applications may yield different preferences for shield grounding.
2) As a reminder (and previously discussed in ack's system thread) different foils provide optimum shielding for different frequencies. In short, mu metal is optimum for low frequencies and copper foil is for mega and gigahertz frequencies.
3) What's next? Easy. I have a bunch of copper foil left over so I will try wrapping my Stealth USB T-select cable and then try some of ack's other suggestions on phono.
4) Tasos, I totally agree that some of our observations and benefits with shielding may be due to the ultra wide bandwidth design of Spectral electronics and/or MIT cables and their networks. But it may also have to due to the proximity of placing these network boxes nearer or farther from contaminating radiation. In my case, the SHD boxes are inside my equipment cabinet and located immediately next to my pre-amp which is only 1 shelf beneath my DAC. Perhaps if they were placed further away, the benefits of shielding the network boxes may have been significantly less or perhaps none at all. Still, these experiments are easy and cheap enough to perform with the potential of significant benefits in return so why not?

 

[Tango]

Dear Sir,

Could you pls post a picture of the mu metal box covering your MIT network box.

Is it one of the two boxes in the pic you posted?

Kind regards,
Tang

 

[marty]

Dear Sir,

Could you pls post a picture of the mu metal box covering your MIT network box.

Is it one of the two boxes in the pic you posted?

Kind regards,
Tang

Tang,
The pics were posted above in the OP. Each of those is a box for one network (1 each for left and right channel). The box was made by taking mu metal foil, and then lining it with copper foil (with self sealing adhesive placed directly in the mu metal surface) and then just folding the combo flat foil into the shape of a box (~4.5" x 3.25" x 10") with one end closed by folding the end flaps. All is held together by duct tape. The MIT network box just slips inside the box that you see with its wires protruding from the open end.

The materials were sourced here:

copper foil: 10 ft of 6" wide foil: https://www.amazon.com/gp/product/B01F6JZITC/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
mu metal foil; 2 linear feet of 15" wide foil: https://www.amazon.com/gp/product/B00K0QKI8S/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

Please advise if you need more specific guidance.
Marty

 

[ack]

Here are a couple of things I dug up for you Marty:

1) An older discussion on this subject here http://www.whatsbestforum.com/showt...cts-of-electronic-noise-reduction-in-a-system

2) If your phono has multiple inputs, a better solution than caps on the unused inputs is the ack-plug , basically an RCA plug with a resistor in it, and depending on your phono, watch your noise go further down (the XP-25 benefited) - http://www.whatsbestforum.com/showthread.php?8786-Custom-cartidge-loading-resistors (and I would never use those caps that short-circuit any input)