I think I have a ground loop problem that is proving very difficult to properly identify. I’ve not given up yet, but in the event of having to resort to a Ground Loop Isolator on my AV input, does anyone have recommendations, as I understand that the quality varies greatly in terms of signal/sound degradation? I have read decent reviews of Earthquake which is readily available at £30-40 and Jensen which does not have a UK distributor and costs closer to £200.
Ifi make a ground isolator. Not cheap though.
Is it not simpler just to troubleshoot the issue and root cause it? If you have a loop then you have a 50Hz huml There can only be so many possible culprits.
What device is feeding into your AV input?
Surely earthing that would be simple enough and hopefully cure the hum?
I have 4 AV inputs (Sky Q, Oppo BD, Amazon Fire and Apple TV) into a Lumagen Radiace Pro Video Processor then into an Arcam 850 AV amp. I have a long interconnect running from the AV amp to my NAC 552DR pre-amp. I am confused because using a long mains extension cable to run the AV amp into the same Chord PowerHaus block as the Hi-Fi does not make any significant difference.
Do all sources have 3 pin plugs or are some unearthed?
Similarly, does the Arcam use a figure eight plug for the mains input, or a three pin earthed mains lead input?
A Google search suggests it uses a 2-pin input mains lead, which is more than likely why you get a hum.
If this is the case, my first thought is to earth the metal casing of the Arcam to known earth point, such as the earth pin of a mains plug (if you’re in the UK this is dead easy) .
I have a similar issue if I connect my 252 pre-amp to my Anthem AV amp, which only uses a two-pin mains connection. Earthing the Anthem amp casing cured my problem.
I can’t remember the last time I had a ground loop problem, and certainly never to the point that I’ve needed a ground isolator, or even a ground lift switch, but it was probably 3 decades ago. I have never had that many sources but I can imagine things are getting pretty complicated these days, even with well-designed equipment. The reason I am chiming in is to say a word about Jensen. Their head, or maybe one time head as he now also has THAT Corporation, Bill Whitlock, is one of the world’s foremost experts on ground loops and Common Mode noise in systems. It’s what Jensen was set up for with its transformers and what the THAT Corporation was set up to do electronically. He understands this aspect of signal integrity so well it’s almost instinctive. I can assure you that even good (or great) designers, who will inevitably have put a lot of thought into their grounding schemes, still somewhat cross their fingers when they come to connect things up (at least I do, certainly). It’s an incredibly thorny area, to the point that designers who hear hum, or have it show up in measurements, can be left just as puzzled as you are at the moment.
Those are a few reasons to go with Jensen; there is literally a lifetime of experience dedicated to this one sole problem and presumably many others at Jensen who understand it just as well. The other thing I wanted to suggest was to read Bill Whitlock’s articles on the topic which are available on the Jensen website, or at least used to be. (If they are not - I should have them here and can send you copies.) They are well-written, clear and are deeply impressive. They’re also quite amusing, though I shan’t ruin the fun by telling you here, but it’s very “real life”. They may not provide you with the solution - there may not even be one when connecting to an unknown grounding scheme - but they will certainly improve your understanding and give you a broader framework to work with. (I think that’s true at all levels of expertise.)
Finally, I’m not sure this is an area where one can be guided by reviews. I don’t know either of the products but I do know it’s multi-faceted. I suspect - though I could be doing some reviewers a disservice - that their main concern will be more whether it works or not than the degree of signal degradation. I would definitely want to know that the reviewer has some sort of background in electronics and magnetics - which some of them do, of course. This isn’t really a “this one sounds better” area.
PS. Actually, let me modify that “this one sounds better” statement. It obviously is, but it’s heavily reliant on things that can be objectively measured and need to be properly understood, some of which are not at all easy, and a lot of which have been forgotten. It’s a bit like output transformers in old valve amps, the quality of which largely defined the quality of the amplifier. If you build a copy of one today you probably shouldn’t expect it to sound the same or as good as the original.
The best ground loop isolator is cutting the loop, though that can be painstaking, requiring tracing all ground connections for each box, including checking the ground path on each attached cable. (As a general rule no box should have more than one connection to ground, though there can be exceptions.) if no loops and there is still hum then look for a box or cable that is not grounded and try connecting to ground, as lack of grounding rather as well as a ground loop can result in hum.
Thanks for all the advice.
I have 4 AV inputs into a Lumagen Radiance Pro Video Processor (round power lead) and then into an Arcam 850 AV Amplifier (2 pin). The AV inputs are Sky Q (2 pin), Oppo 203 (3 pin), Apple TV (2 pin) and Amazon Fire Cube (round power lead). I have tried disconnecting the two satellite connector leads from the dish without any benefit.
I have three inputs into my NAC 552DR / NAP 500DR - a long AV lead from the above Arcam 850 AV amplifier via a twin RCA to DIN adapter with Unity Gain enabled, dCS Rossini Apex Player and Clock (both 3 pin) connected via RCA and Phono (Rega RP8 and Moon 110LP Phono Stage) connected via a twin RCA to DIN interconnect. I understand that Rega turntables are earthed but not via a conventional earth lead. The Moon phono stage has an unused grounding connection. I have read it is possible to add a grounding lead to Rega turntables.
Please jump to point (1) and start from there. Then return to my waffle below if you want some more reading.
I am not familiar with any of your components except the Apple TV.
If I was in this position, I would disconnect everything and slowly add one item at a time to see when the hum would kick in.
Though maybe we can try to do something a little less drastic.
I would use quality power boards that have a star point earth connection. Others may jump in and recommend a particular manufacturer.
As an example, my system is much similar. I have two power boards, and only one is connected to an inlet power point. My first powerboard cost about $80 AUD from eBay. All my Naim equipment is connected to this power board which has no filtering except for spikes. No surge protection. Pretty basic.
Then I have an expensive power for my Linn and phono pre-amplifier, Phono power supply Lingo 4 power supply. I believe this power board does have a star point, earth. This power board is then plugged into an outlet on my first power board, which all my NAim equipment is connected to. Therefore there is only one earth path. Since all the Naim equipment is connected to the first power board, all earth potential voltages should be at the same level, and there should be no earth loop paths.
I do have plans to add an ND5 XS 2 one day which may complicate things, though I think I will be alright. There is an earth lead from the TT to the phono pre-amplifier.
All interconnects are Naim except the phono outputs, which are RCA.
This might be confusing.
Start with all the Naim equipment fed from one power board and that power board fed from one power point outlet.
Have all none Naim equipment fed from a second powerboard and that power board connected to the first power board.
Check to see if there is any hum?
Mute the amplifier, then connect one input. Turn that piece of equipment on and then unmute the amplifier.
Repeat step (4) for each piece of input equipment.
My first powerboard brand is a Belkin with eight outlets.
My second power board for the TT and all phone equipment is a Thor SMARTBOARD 8 with active dynamic tracking (whatever that is). I just purchased what the dealer recommended.
All m power IEC connecting cables are ISOTEK EVO3 sequel power cables (2 metre C13).
The only inputs I have to my Naim XS2 are the CD5 XS and the output of the phono amplifier RCA connectors, which is an OAD Ultrafidelity. Interconnect is made by Wirewound.
My power outlet on the wall is a double power point behind the stereo shelving. Though I only use one of the outlets. The second outlet on the wall is used for the FOXTEL IQ4, which is not connected to anything else other than the wall-mounted TV. The wall-mounted TV is fed via an internal wall power cable to a separate outlet behind the TV from the power point, which feds both the Naim and FOXTEL IQ4.
I hope this makes sense.
Picture of setup.
I am happy to chat online as long as it takes if I can help.
Mitch in Oz.
Yes I think a few terms are being mixed up, and with some manufacturers being inconsistent doesn’t help.
Signal return and ground/earth are not usually the same thing. If they are combined in a manufacturer’s product with no option to separate, it can cause interoperability issues between manufacturers and induced voltage ground loops.
Breaking the ground loop connection can in some cases reduce SQ, especially if the signal return has to be through the mains, which is not optimal for audio signals.
Ideally in an audio setup there should be only ground /earthed device… so called Star earthing… but not all manufacturers follow the same approach.
Ultimately I say if your preamp is not floating ground for each audio input … and Naim preamps definitely not, as they are designed for one and only one ground/earth signal return source to be connected at once… historically the CD player, and typically now Naim sources have a ground / float switch to ensure only one earth / ground in a system. I would suggest if you have ground loops it might be the source is in your system incompatible. One technique that I have seen used is a series resistor in the signal return, this can make the inductive loop sufficiently lossy that no current is induced… also an audio frequency bypass capacitor could be used, but again it tends to rob very low bass frequency currents. The inductive ground loop will pick the dominant magnetic field in your house, which is usually the mains frequency and its harmonics.
In terms of the sources feeding the 252, you only really have one outside of your Naim system; The Arcam 850.
If you have nothing plugged into the inputs of the Arcam, does the buzzing still appear through your Naim system?
If the answer is yes, make an earth connection between the casing of the Arcam.
A simple single wire screwed to a casing screw on the Arcam to a known earth.
UK wall sockets screws are earthed for example, so you can loosen a socket screw and connect your earth to that.
The above described earthing takes minutes to try and I suspect might well cure the buzzing.
Or easier and safer if unsure and you want to try, buy a standard 13A plug and connect the earth wire to the earth pin (longer pin at right angles to the other two pins) and simply plug into a socket. The wire should be insulated so no risk of touching either of the other pin connectors. And ideally a single core, or if using one core of multi core cable ensure the others are cut short with no wire protruding anywhere where it could with movement reach the other connectors.
In fact the way to do it is connect a wire to earth like that before connecting to the case, then while the system is on and humming touch the bare end on bare metal of the casing (often a screw or right beside the screw if paint has lifted, to see if it makes a difference. And no harm in doing that with casing of everything else while you’re at it.
I recommended a RDL AV-HK1 audio isolation transformer to someone a few months back. It solved their hum problem (AV hard ground and Naim 500 series system).
It was put in line with the AV input to the NAC 552.
I do not know the sound quality having not heard myself.
That is a last resort… you are decoupling the signal return, but it will impact audio performance to a degree, certainly lower end performance to some extent, but could be very much the lesser of two evils… and is a valid option if all else fails and your devices are otherwise incompatible with each other.
The aim I suggest is to make the inductive loop lossy at 50 Hz and below whilst having minimum effect on higher audio frequencies… say from 100 Hz and higher.
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