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.