My setup is reasonably simple, but there was a ground loop hum from somewhere. Most of my equipment is very close together, including the router and sky box and all cabling, so maybe noise is induced by that.

I have a resolution Audio Cantata 2.0 which feeds a BSS fds334T DSP controller via XLR cables.
The BSS has 2 pairs of outputs that then feeds a pair of PMC AML1’s and a pair of MC2 MC450 amplifiers that I run bridged to feed a pair of subs. These don’t get turned on that often these days though.


I thought the fds was introducing noise as it’s more a Pro Audio/studio piece of gear and people have often turned their noses up at the thought of using such a piece of equipment in my Hifi. The reality of it is though, I have such a huge peak in bass around 40hz in my room, that bass driven music was awful to listen to, drowning out the midrange. I use REW and my ears to get what sounds like a reasonably flat response to 30hz without the subs and 5hz with the subs.

Adding this Ground box with just 1 cable to the unused RCA digital input of the dac lifted system performance quite substantially, but didn’t reduce any hum.
I then started adding extra cables to the Ground box to see if anything changed and that’s when I noticed the hum disappeared.

The next test was to shield all the ground cables to see what effect that had.
As soon as I removed the first cable, which happened to be the Dac’s rca analogue out for the left channel, the hum returned.
I have since put all the newly shielded cables back in place and the hum disappeared again.
I will give this a few days of listening and settling to see if anything changes.

The first box is approximately 23 x 10 x 10cm.
The second box is around 20 x 20 x 12cm.

I’m tempted to try it, but want to give the shielding a few days to settle and get accustomed to the sound.
My plan is to try the new 3 post box in place of the existing box, then I will make up some new cables with copper lugs to go to equipment chassis. I will then use one of the boxes just for the chassi connections.

Jazz Nice.... Thats a great example if you don't apply these tweeks correctly, like most things in life,you have to have patience,it's easy to over eggs things.

l have a good feeling about your 3 way box Matt. The bad news.... lt's mean. buying larger amount of Magnetite.

Damien

Sums up that OMG moment I described on an earlier post when on your advice I removed the EMI/RFI reducing ferrites from my digital leads everything opened up deeper more fluid bass, mid range more expressive treble sharper with more fine detail but not harsh, more ambiance a wider/deeper soundstage it went from recorded music to a musical performance I was suddenly in Ronnie Scotts with Norah Jones  , my OTA Quad 57's playing dedmau5 electronic music with no inhibitions.  The RFI/EMI was masking the true nature of the system before the copper foil when the ferrites on the coax were damping & rolling off highs, mids & lows.  I will be forever grateful  

I did try magnetite and quite a few others pezioelectric materials (8 in total), all of which had an effect to a greater or lesser degree, none really make the magic bullet status for ourselves, however it's really nice to see chaps going that extra mile, respect Matt

A bit of an update on the Ground boxes.

I tried the new, larger box, even though it was just over half full as I waited on more Magnetite. Something was missing, even though things seemed quieter in the system. I was missing the air and 3D space that these ground boxes bring.

As you can imagine, this annoyed me, as making the new box was quite time consuming. I switched back to the first box and still something was missing and both boxes sounded similar and lacking the air, so I decided to take a couple of steps backwards and remove most of the RFI shielding off the cables and keep the first box connected. This worked and things were sounding good again.

The extra 2.5kg of Magnetite arrived today, so I added about 2.3kg of this to the larger box, along with the small quantities of the other materials to keep the ratios as close as possible to the first box. The large box now weighs 6.3kg vs the first box of around 3.5kg.

I also reworked the cables a little so that I have 2 cables, each with an rca and a DIN connector. These connect to left and right analogue outputs of the DAC and 2 empty MIDI connections on the DSP. This is what solves the ground loop hum.
I removed the XLR ground cable from one of the above 2 cables and made it into its own cable with an extra core of wire, so it totals 4.5sqmm. I had to crimp the 2 cores together at the XLR end as only 1 core would fit into pin 1 of the XLR. Making the XLR for the AES input of the DAC into its own cable now means I am able to separate Analoge and Digital into 2 separate Ground boxes if I like as a future experiment.

I also made this link cable to allow me to connect the 2 Ground boxes together to see if more mass benefits things further.

Untitled by Matt Hoyle, on Flickr

This is the large box with the extra Magnetite.

Untitled by Matt Hoyle, on Flickr

I'm please to say that the larger box outperforms the first box. Much better P.R.A.T, detail, bass resolution and power. Its like the noise level has dropped and sounds like the amplifiers have been given more grip over the speakers.

Since the weekend, I’ve had the first ground box hooked upto the earth connection on my ifi AC ipurifier that is connected to my mains regenerator. The second box is still connected to the Dac and dsp as before.
I’ve really been enjoying the system and have been playing it for a few hours this evening, also with no issues with BubbleUPNP.

I have now taken the ground box off the ifi and linked it to the 2nd ground box to see how this performs.

And I spoke too soon, My Dac just lost its connection to BubbleUPNP 😂

So, adding Ground box no.1 to the Earth on the ifi filter increased resolution notably, but not near the extent of putting a ground box on signal ground duty.

Next was to link the 2 Ground boxes together using the cable I made which contains 3 cores of cable. One core being the Elec Audio 2.5sqmm OCC and two cores being AliExpress 2.0sqmm 6N OCC copper cable, giving a total of 6.5sqmm.

Linking the 2 boxes together on signal grounds gives much better results than 1 box on signal and 1 box on Earth duty.
I need to do more listening tonight, but what I heard yesterday was another layer of fine detail being revealed that was previously buried in the mix.

I will leave the setup like this over the weekend, then next week at some stage I will separate the analogue and digital between the 2 boxes to see what that achieves.

I’d ordered a USB plug to make into a ground cable to add to the Dac, but it’s gone missing. The tracking said it was delivered on Monday, but it’s nowhere to be seen.