Copper Sleeve over IEC

A gent over at AA suggested using 3/4" copper union (sleeves, couplers) over a CD players Digital inputs and outputs.
He also suggested to use what he called digital "terminators" , which I call shorting plugs.

I was not sure about adding a shorting plug to an output and it made me nervous even trying it.
But, after some assurance from people who sell the digital shorting plugs that they were ok to use on Input and outputs on digital , I gave it a try.

I tried metal Digital shorting plugs on both the coaxial input and output on my Cary 306 SACD Player and it did indeed make a difference. The soundstage and center image improved.
I was very suprised that the shorting plugs will work both on Input and output on digital.

But, when I added the 3/4" copper sleeves over the metal shorting plugs, it dulled the sound, so no go for me on the use of copper sleeves over the digital shorting plugs.

Perhaps if the shorting plugs were plastic then the copper sleeves might have made an improvement...

Ozzy, I am not at all surprised with what you found, but shorting an output, if it is on, is a no-no.

We've got big rolls of 36 gauge copper foil at work, so I've tried cutting strips of this to experiment with. With foils, you can add layers to try different amounts of shielding. It can be tightly wrapped & pinch formed to close around the back of the ac plug. I must say I do hear some changes to the sound of the cd player & dac with added shielding on the iec plug. I'm not sure that I like what it does on my Marantz Sa11S1, but it's a definite positive used on my dac.

I placed a piece of copper foil coupled with a brass weight over the first plug socket on my power strip. You can hear the noise level drop. This strip is for my digital source only.

There was no improvement when I moved the copper/brass to the middle or end of the strip.

Tbg, Thats what I thought that the shorting plugs were not to be used on outputs.

So, I sent an email to the gent selling some of these shorting plugs on Audiogon, here is a portion of his reply.
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"Hi, Thank you for your inquiry. The digital-terminators can be uses on in- and outputs. The analog-terminators "shorties" can only be used on inputs - never on outputs! "

Then I dug up a review of the Digital Shorting plugs.

From a review of the digital shorting plugs.
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"Now this one is completely new to me – both the concept and the application. The explanation for its effectiveness is somewhat different; it aims to combat not RFI but internal ‘reflections’ from unused S/PDIF in/outputs on CD players, transports and DACs, these claimed to interfere with the main output signal"

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I had some old RCA shorting plugs , some marked Digital and other analog. I used the the digital ones in both my CD Players input and output and it was a marked improvement. Putting copper sleeves over the Shorting plug dulled the sound.
When I pulled the copper sleeves off of the shorting plugs the CD player glitched and froze.
I unplugged and replugged the player and all is well, but I am not using the copper sleeves over the shorting plug..