Background noise problem- Revisited

[incans]

WiiM Device: WiiM Ultra (Firmware 5.2.734250)
Network: Ethernet (hard-wired)
Speakers: Focal Shape Twin (active)
Subwoofer: B&K P12-300SB-PR
Sources: Samsung S95B (HDMI ARC), DLNA Streaming (hopefully)

My first post on the forum (RCA to balanced speakers - background noise problem) was about a noise problem with my new Wiim Ultra.

That situation was complicated by 2 factors- fault in one of my active speakers that was causing noise in that channel, plus the fact that those speakers (actually active studio monitors) only had XLR inputs, so an unbalanced-to-balanced connection was involved.

I now have new speakers. While the Focal Shape Twins are active studio monitor like my previous KRKs, these are (a) brand new; and (b) have RCA inputs so the system is a classic domestic unbalanced setup. I have also changed the physical arrangement so the Wiim, speakers, and sub are all on one wall with shorter cables. (the longest lead is a 5m shielded RCA to one speaker)

Problem: the noise issue is still there!

It's not as bad as it was before, but it is still the case that-

• When there is no music playing there is a continuous mains frequency (50Hz) background buzz coming from both speakers. It's quiet, but I can hear it sitting over 4m away in my normal seating position, so it's not quiet enough to be something I can ignore.
  
  Note I am pushing 70 myself and my hearing is nothing special. The noise would definitely be audible to anyone with moderately good hearing using these speakers in their designed role as nearfield monitors sitting maybe 1.5m away.

I am sure the Wiim is the source-

• With the RCA leads disconnected the speakers are silent
• With the speakers powered on but the Wiim turned off there is silence
• With Wiim and speakers powered up, as before there is an audible "stepping" sound overlaid on the mains hum if the volume setting is raised or lowered using the Wiim app. The same noise is audible when using the front panel volume knob, so I don't think this is related to RF breakthrough. It seems more like output filtering or isolation problems in the Wiim

My question now is whether I have a faulty Wiim Ultra that needs to be returned, or is this an inherent design problem?

It would be very helpful to know if anyone else has experienced something similar, or are your Wiim units as silent as the grave when they are supposed to be?

 

[huw]

1. I ran a 30ft extension lead to another part of the house that is on a different ring main (socket outlet circuit) and powered the whole system from there. Finally, silence!

To be clear - when you powered all devices (speakers, WiiM Ultra and sub) from an extension lead the noise was gone? When you had the problem were all devices also connected to a single socket?

Meanwhile, if using an external DAC does typically deal with the problem, then WiiM should be asking themselves how it is that DAC manufacturers can design products that successfully filter out mains noise, but they (WiiM) can't?

It's not the DAC filtering the noise it's that you can put an *optical* connection between the Ultra (connected to the sub which is grounded) and the speakers (which are also grounded) breaking the loop.

 

[dominikz]

The only thing that's made a major difference so far, essentially eliminating the noise problems, has been to run the whole system from a different mains circuit via a 30+ft extension lead. I think that indicates the primary problem is mains-borne noise rather than a ground loop, a ground loop would surely be unaffected by altering the supply while the local wiring between devices remains the same?

IMHO mains-borne noise shouldn't really be a problem as that would normally be filtered out by the PSU.

Can it be by any chance that on the original mains circuit the ground connection is missing (e.g. it is a 2-pin outlet) or is faulty (e.g. wrong wiring)? That would IMO be consistent with the behavior you are describing.

With a proper ground connection the 3-pin connections of the active speakers and the sub would establish a ground reference for the Ultra as well. Without this you get a floating ground, which means that any induced noise has no ground path - which seems to be the case here based on your descriptions. Lack of ground with class 1 devices (i.e. with 3-prong power cables) can be a safety hazard.

 

[Steve Woodhouse]

I found a reasonably.priced external DAC on eBay. I'm going to give it a try.

Having spent 3+ weeks going round this circle I also logged an issue with WiiM support. Their initial reaction was not terribly helpful. I think we have established by now that "eliminate sources of mains noise" and "find a clean mains source" (not their words but I'm paraphrasing) will work, sure, but they may not be easy or realistic to achieve in the real world.

.Assuming my Ultra is typical of the breed, and several responses here seem to indicate that is is, it seems to have a weakness in dealing with mains source noise, more so than other mainstream products. I'd like to see WiiM acknowledge that, do some investigation, and -

1) Improve future products (and ideally even upgrade the Ultra) to make them better at handling mains-borne noise

2) Come up with some standard recommendations to mitigate the problem for Ultra customers who are running into problems, that don't cost an arm and a leg.

"Get a clean mains supply" isn't a solution, it's a class of solutions up to and including "rewire your home" (and even that might not fix the issue).

Meanwhile, if using an external DAC does typically deal with the problem, then WiiM should be asking themselves how it is that DAC manufacturers can design products that successfully filter out mains noise, but they (WiiM) can't?

You’re confusing ‘mains-borne noise’ with ground loops. Not the same thing. I’ve had my Ultra cranked up to full, my power amp up to full, and my ear to the speaker (with no music playing) and it’s silent.

You have a ground loop, which you’ve both identified and fixed with a long extension cable. You’ve been given advice on more permanent and domestically acceptable ways to fix it. And it’s been explained that ground loops can happen with expensive kit, and has little to do with the standard of the equipment.

Shielding from general mains noise is easy and cheap, and clearly not something WiiM can’t/don’t do - the noise level on the sub-£100 Mini is pretty much zero.

 

[anonyless]

I found a reasonably.priced external DAC on eBay. I'm going to give it a try.

you can buy a new SMSL SU1 on Aliexpress for around 70 USD

Meanwhile, if using an external DAC does typically deal with the problem, then WiiM should be asking themselves how it is that DAC manufacturers can design products that successfully filter out mains noise, but they (WiiM) can't?

the workaround here (it's not a solution) is to use the optical output on the Ultra instead of the RCA . it's not about the DAC itself.
also in my case, I was using 3e audio A5 amp that uses an external 2 prong power supply (great amp). when I replaced it with the WiiM Vibelink that has internal PS with 3 prong connector, the hum noise was gone , even with the RCA output on the Ultra

 

[HansD-NL]

You’re confusing ‘mains-borne noise’ with ground loops. Not the same thing. I’ve had my Ultra cranked up to full, my power amp up to full, and my ear to the speaker (with no music playing) and it’s silent.

You have a ground loop, which you’ve both identified and fixed with a long extension cable. You’ve been given advice on more permanent and domestically acceptable ways to fix it. And it’s been explained that ground loops can happen with expensive kit, and has little to do with the standard of the equipment.

Shielding from general mains noise is easy and cheap, and clearly not something WiiM can’t/don’t do - the noise level on the sub-£100 Mini is pretty much zero.

Agree. After all the things that the OP tried there must be something fishy with the ground connection on the circuit (wiring/connection to the panel) where everything was originally connected to. The test with the extension lead confirmed that.

 

[jed1]

I did make up a grounded mains connection for the WiiM, with a 3 pin plug and a ground wire that connects to the Ultra's ground pin.

The effect was a minor improvement, roughly equivalent to (as mentioned above) the effect of me touching the casing of the WiiM while it's in operation.

The only thing that's made a major difference so far, essentially eliminating the noise problems, has been to run the whole system from a different mains circuit via a 30+ft extension lead. I think that indicates the primary problem is mains-borne noise rather than a ground loop, a ground loop would surely be unaffected by altering the supply while the local wiring between devices remains the same?

Try turning off the circuit break that is connected to your audio system and see what other electronics share the same circuit breaker. For audio installation, I use a power outlet that does not share a breaker with non-audio related appliance. Refrigerator, microwave oven, washing machine, fluorescent/led lamps can inject noise to the audio system that shares the same breaker.

 

[incans]

To be clear - when you powered all devices (speakers, WiiM Ultra and sub) from an extension lead the noise was gone? When you had the problem were all devices also connected to a single socket?


It's not the DAC filtering the noise it's that you can put an *optical* connection between the Ultra (connected to the sub which is grounded) and the speakers (which are also grounded) breaking the loop.

I originally had all the stereo audio kit connected to a single socket via a multi-way IEC splitter cable arrangement. Partly for convenience so I could turn everything on/off from a single point, but also (perhaps naively) thinking this would help establish a common ground reference.

I currently have the Wiim itself connected via a separate socket to the other equipment, but this 2nd socket is only about 10ft. away on the same ring main. The physical layout of the room and wiring only gives me these two sockets as options, without moving the kit to another room, or house wiring changes.

Moving the Wiim to a separate socket was done for convenience while I was testing out a temporary mains lead with a cobbled together ferrite bead on live+neutral and an earth wire.

After spending time modifying cables I have found that-

1. A grounded 3-core cable mains cable attached to the Wiim ground post significantly reduces (but does not eliminate) one type of noise, a high pitched whine. When this occurs it's audible even the Wiim is powered off (but the speakers are powered on). Linking the speaker RCA shield to the Wiim ground pin has no effect on this.
2. Connecting the shield of the Sub RCA to the Wiim ground pin reduces (but does not eliminate) a different noise, a distinctly mains hum based buzz with a 50Hz fundamental.

 

[incans]

It's not the DAC filtering the noise it's that you can put an *optical* connection between the Ultra (connected to the sub which is grounded) and the speakers (which are also grounded) breaking the loop.

I understand the purpose of introducing the optical connection to break the ground loop. However an external DAC needs a mains power supply itself (unless you are going to go full audiophile hair shirt mode and run it from a battery). The fact that (by default) the Wiim is ungrounded/floating has not saved the situation, so is this necessarily going to be better?

Does this rely on segregating the other grounded devices? In my case currently the only other grounded device that would be isolated is the sub (which I can see might be relevant), but in a more complex setup there could be other grounded devices such as a CD player on the "quarantined" side of the optical break in the earthing.

 

[incans]

IMHO mains-borne noise shouldn't really be a problem as that would normally be filtered out by the PSU.

Can it be by any chance that on the original mains circuit the ground connection is missing (e.g. it is a 2-pin outlet) or is faulty (e.g. wrong wiring)? That would IMO be consistent with the behavior you are describing.

With a proper ground connection the 3-pin connections of the active speakers and the sub would establish a ground reference for the Ultra as well. Without this you get a floating ground, which means that any induced noise has no ground path - which seems to be the case here based on your descriptions. Lack of ground with class 1 devices (i.e. with 3-prong power cables) can be a safety hazard.

The possibility of a fault in the earthing of the mains supply is a disturbing idea. I don't really want to have to call out a pro electrician to test the wiring, but I will see if I can do some preliminary testing myself. If there's any indication of a possible problem i'll have to get it looked at.

 

[huw]

I originally had all the stereo audio kit connected to a single socket via a multi-way IEC splitter cable arrangement. Partly for convenience so I could turn everything on/off from a single point, but also (perhaps naively) thinking this would help establish a common ground reference.

Yes it should. That's why I wondered if it was something that also changed when you used the extension lead. Agree it sounds like the issue is with the circuit everything was originally connected to.

 

[Nanook]

A grounded 3-core cable mains cable attached to the Wiim ground post significantly reduces (but does not eliminate) one type of noise, a high pitched whine. When this occurs it's audible even the Wiim is powered off (but the speakers are powered on). Linking the speaker RCA shield to the Wiim ground pin has no effect on this.

We once had a problem with several ICE power modules in a 3-way active speaker. The cabling did have some crosstalk and the beat frequency got audible. The pitch changed during warm-up.

Eventually some energy from the SMPS finds its way into the PE wiring and this could interfere with some other SMPS.

- Does this high pitched noise / tone disappear when you switch off one of the speakers?
It may need to switch off the sub as well.
(keep them plugged such that the PE connection is given for all units).

Regarding the hum (and harmonics that are audible even better) I suspect ground loops - be it just between the two speakers and the sub.
Having this interference with the WiiM switched off almost proves this suspect.

The speakers do they have a 3 prong plug (likely class I unless it's "functional grounding") or a 2-prong one?
A photo of the mains inlet with all the symbols around would clarify a lot.

I don't understand that companies build active speakers with single-ended (RCA) input only. A differential input (XLR or TRS) do not cost a lot and you can solve almost any interference issue with a proper cable (i.e. cold connected to Gnd on the RCA side of the cable).

 

[Nanook]

I just see that the new Focal active speakers have XLR inputs:

Shape Twin - 2,5-Wege-Überwachungslautsprecher | Focal

Shape Twin, 2,5-Wege-Überwachungslautsprecher : Unsere professionellen Monitore sind von Anfang an so konzipiert, dass sie das Tonsignal unverfälscht wiedergeben. Diese Monitore werden sowohl den Anforderungen großer Studios als auch kleiner Hörräume gerecht.

www.focal.com

Why not connect these XLR inputs properly to the RCA outputs of the WiiM just like described in the initial thread?

K

Post in thread 'RCA to balanced speakers - background noise problem'

Oct 13, 2025

Not sure that will be of any help but I have been using Wiim Ultra's line out to my fully balanced power amp (hypex ncore) and it's dead quiet, not a single pop, noise or whatever. Basic RCA to XLR cable (cold to shield) but much shorter, 40cm as I don't need any longer.
For the sake of principle, I used balanced cable for each channel and connected cold to shield at RCA's end, this was my understanding of hypex recommandation. Maybe completely useless, no idea.

• Kro

• 

Or did I miss something?