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?

 

[Wiimer]

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?

I'm not currently using the Ultra's line-out, but I don't recall hearing any noise. Could you connect another device to the Focal speakers and see if you hear the same noise?

If you don't have another device to connect, you might also consider connecting the TV's headphone output to the speakers.

 

[jed1]

50Hz hum seems to be a ground loop. Source of such noise can be TV, powered subwoofer, ethernet or WiiM itself. I would try;

1. Ground WiiM Ultra with phono ground to main ground
2. Use WiFi instead of ethernet
3. Disconnect TV or use TV's toslink output instead of HDMI ARC
4. Disconnect subwoofer (power and signal)

Alternatively, I would try an external balanced DAC with TOSLINK connection to WiiM Ultra's Optical output. This will guarantee electrical isolation.

I use studio monitors and subwoofers. I use WiiM Pro Plus with an external DAC that have optical input and balanced output and experience no noise issue (TV via TOSLINK).

 

[incans]

50Hz hum seems to be a ground loop. Source of such noise can be TV, powered subwoofer, ethernet or WiiM itself. I would try;

1. Ground WiiM Ultra with phono ground to main ground
2. Use WiFi instead of ethernet
3. Disconnect TV or use TV's toslink output instead of HDMI ARC
4. Disconnect subwoofer (power and signal)

Alternatively, I would try an external balanced DAC with TOSLINK connection to WiiM Ultra's Optical output. This will guarantee electrical isolation.

I use studio monitors and subwoofers. I use WiiM Pro Plus with an external DAC that have optical input and balanced output and experience no noise issue (TV via TOSLINK).

Thanks for the suggestions.

With the new physical arrangement of my gear I can't easily connect to the TV via HDMI. The temporary setup is a TOSlink lead trailed across the floor under a cable cover, so isolation is sorted in that area.

My current setup for music is serverless, just a USB stick, so i can live without the Ethernet connection at least for test purposes.

The other two ideas are interesting, especially re. the sub. I will test and report back what I find.

 

[slartibartfast]

Thanks for the suggestions.

With the new physical arrangement of my gear I can't easily connect to the TV via HDMI. The temporary setup is a TOSlink lead trailed across the floor under a cable cover, so isolation is sorted in that area.

My current setup for music is serverless, just a USB stick, so i can live without the Ethernet connection at least for test purposes.

The other two ideas are interesting, especially re. the sub. I will test and report back what I find.

Is the sound coming from the speakers or the sub? If the sub then maybe contact BK, they supplied me with a replacement mains lead with a DC blocker.

 

[incans]

Is the sound coming from the speakers or the sub? If the sub then maybe contact BK, they supplied me with a replacement mains lead with a DC blocker.

The noise is coming from the speakers. Update on further testing below.

 

[incans]

UPDATE

Results of further testing below. Note that while i'm fiddling around with the connections on the back of the Wiim my ear is right next to one speaker, so i can pick up changes quite effectively.

1. Having the sub connected to the Wiim and powered up increases the volume of the quiescent hum/buzz (maybe doubling the level). Leaving the sub disconnected means the hum is barely audible at 4m from the speakers, but still audible within 2m.
2. I originally had the Wiim placed on top of the sub (actually on a glass protective cover that sits on top of the sub itself). However moving the Wiim off the sub has no appreciable effect on the noise. I think this suggests the issue is down to noise in the signal leads and not induced interference (EMI from the sub power supply)
3. Connecting the optional ground pin of the Wiim to the grounded sleeve of an RCA connector that goes to either a speaker or the sub makes no difference to the hum. Note: I'm not sure this fully covers the "ground the Wiim and the phono ground" point. Directly connecting the Wiim frame ground to the earth provided by the mains outlet means making up a new 3-core power lead for the Wiim, which I might try next).
4. I discovered while testing that if I touch the outer casing (top or side) of the Wiim with my hand the level of hum drops noticeably, to maybe half the volume. I have no idea what this tells us, maybe the capacitance of a human body is reducing ripple voltage?
5. If I use an alternative audio source to bypass the Wiim the hum is not present. I used an old phone which has a headphone jack, plus a 3.5mm jack to 2xRCA adapter to connect to the existing RCA speaker leads.

and finally-

1. I did some poking around with a multimeter, using both DC and AC modes.The only thing of note I found was that if used the meter leads, with the meter in AC node, to connect from the Wiim ground pin to the "hot" centre pin of the sub lead (with the shield of the sub lead not connected at the Wiim end) I got a solid (and loud) 50Hz hum from the sub, with the meter reading about 6.8V.
   
   I am not an electrical or audio engineer, so i'm not sure if this signifies anything, but I wonder if it indicates that there is a substantial amount of mains hum injected into the Wiim's notion of what constitutes frame (and signal) ground. I guess the receiving device is supposed to respond only to the difference between the hot and cold (live and shield) voltages on the signal leads, but if those receiving devices are imperfect at rejecting common-mode ripple, a hum might be the result?

 

[incans]

UPDATE 2

Finally some progress-

1. I took my Wiim Ultra back to the dealer (Richer Sounds) and was able to test it out in their demo room. No noise issue.
2. I brought the unit back home, and (a test agreed with Richer Sounds staff) rearranged my setup so the Wiim was on the opposite side of the room from the sub, just in case interference from the sub power supply was a problem. No change, the noise was back again as loud as ever (I made a recording using my phone but not sure if there's a simple way to post the audio file here)
3. 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!

I think I now know 2 things-

1. I have a source of mains-borne noise in the ring main that feeds the sockets in my living room, which is pretty annoying when that's where the music listening happens!
2. IMHO a device with a switch-mode power supply like the Ultra ought to be extremely good at rejecting or filtering out mains-borne noise, and it seems that the Wiim is not very good at that. Note- I have been using my Samsung OLED TV and Sennheiser soundbar in the same room on the same circuit for 2+ years without any issues, it's only the Wiim that is having a problem.

I am now going on a hunt for a rogue device that might be injecting noise into the mains. It's unfortunate that the living room is fed by the circuit with the most devices plugged into it, but the "bad device" scenario is preferable to the alternative that the house wiring itself has a fault, because that's a much tougher thing to fix.

Meanwhile I may go back to Richer Sounds and ask to swap out the Ultra for another unit, just to verify that this is a common limitation of these devices, and not just my particular device.

 

[Burnside]

Before those more knowledgeable and experienced in these matters jump on me from a great height, might some cheap ferrite cores on the mains leads help?

 

[hgo58]

UPDATE 2

Finally some progress-

1. I took my Wiim Ultra back to the dealer (Richer Sounds) and was able to test it out in their demo room. No noise issue.
2. I brought the unit back home, and (a test agreed with Richer Sounds staff) rearranged my setup so the Wiim was on the opposite side of the room from the sub, just in case interference from the sub power supply was a problem. No change, the noise was back again as loud as ever (I made a recording using my phone but not sure if there's a simple way to post the audio file here)
3. 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!

I think I now know 2 things-

1. I have a source of mains-borne noise in the ring main that feeds the sockets in my living room, which is pretty annoying when that's where the music listening happens!
2. IMHO a device with a switch-mode power supply like the Ultra ought to be extremely good at rejecting or filtering out mains-borne noise, and it seems that the Wiim is not very good at that. Note- I have been using my Samsung OLED TV and Sennheiser soundbar in the same room on the same circuit for 2+ years without any issues, it's only the Wiim that is having a problem.

I am now going on a hunt for a rogue device that might be injecting noise into the mains. It's unfortunate that the living room is fed by the circuit with the most devices plugged into it, but the "bad device" scenario is preferable to the alternative that the house wiring itself has a fault, because that's a much tougher thing to fix.

Meanwhile I may go back to Richer Sounds and ask to swap out the Ultra for another unit, just to verify that this is a common limitation of these devices, and not just my particular device.

Do you use power line WiFi/Ethernet adapters? These have been seen to introduce noise/hum into the analog circuits of the WiiM.

 

[incans]

Do you use power line WiFi/Ethernet adapters? These have been seen to introduce noise/hum into the analog circuits of the WiiM.

I have identified one source of mains noise, this was a mains socket faceplate unit with a built-in USB charger. Removing that eliminated a persistent sharp-edged 50Hz buzz, plus some random noise glitches, at times when the WiiM output is active but the audio volume is 0 or very low.

However this seems to have unmasked a higher frequency constant buzz, plus bursts of actual tone. These are very quiet but the buzz in particular is really insidious, it seems to drill into your brain and makes listening to quiet passages almost painful, even though you can only consciously hear it if you concentrate hard, or get closer to the speakers.

Yes I do use Powerline adapters (TP Link), and I was suspicious if these, but I unplugged the lot (1 master/hub and 2x 3-port client units) and it didn't make a material difference.

 

[incans]

Before those more knowledgeable and experienced in these matters jump on me from a great height, might some cheap ferrite cores on the mains leads help?

Well my best "audio fix" so far has been a bog standard 30ft outdoor extension lead trailed across the floor, so low-tech solution are definitely on the table.

Do you have any pointers on how to set up a ferrite core filtered lead? (and a source for the cores themselves-,eBay?)

I had started looking at transformer based mains conditioners, but the prices are crazy. I don't see the point in buying the Ultra at under £300, if you need to spend the same again (or more) on a mains conditioner unit. It would actually be cheaper I think to buy an external DAC with balanced outputs from someone like FOSI, and connect that to the WiiM via coax or TOSlink.

But the fact remains that other audio devices (TV and soundbar) work happily in the same room with the same power supply, so unless I happen to have bought a bad unit, it does seem the Ultra has a problem with keeping mains noise out of the signal chain, at least when it comes to the analogue RCA outputs.

 

[Burnside]

Do you have any pointers on how to set up a ferrite core filtered lead? (and a source for the cores themselves-,eBay?)

These or similar wrapped round the power cable(s)

https://www.amazon.co.uk/Innfeeltech-Ferrite-Cores/dp/B0D41F6JHD

 

[anonyless]

by any chance, do you have (any) DAC lying around, that you could test by connecting between the Ultra optical out to your monitor speakers?
i had a very similar issue with the Ultra, and by using its optical output instead of the RCA outputs, it solved my ground loop noise.

 

[incans]

by any chance, do you have (any) DAC lying around, that you could test by connecting between the Ultra optical out to your monitor speakers?
i had a very similar issue with the Ultra, and by using its optical output instead of the RCA outputs, it solved my ground loop noise.

Unfortunately I disposed of my last external DAC (a Cambridge Audio unit) some time ago, so this isn't something I can easily try.

High on the list of appeals of the Ultra were it's low cost and "everything in one neat box" tidiness. A return to a multi-device solution adds cost, and feels like a return to the big stack of stereo gear under the TV that this was supposed to replace.

Having said that, as I mentioned above, purely from a cost perspective an external DAC might be no more expensive than a mains conditioner/filter (which seems bizarre given the comparison of the technologies involved). Given that a DAC is basically just a small subset of what the Ultra does, I was not confident that a DAC would necessarily solve the noise problem, so your experience is very helpful, thank you.

 

[anonyless]

Unfortunately I disposed of my last external DAC (a Cambridge Audio unit) some time ago, so this isn't something I can easily try.

High on the list of appeals of the Ultra were it's low cost and "everything in one neat box" tidiness. A return to a multi-device solution adds cost, and feels like a return to the big stack of stereo gear under the TV that this was supposed to replace.

Having said that, as I mentioned above, purely from a cost perspective an external DAC might be no more expensive than a mains conditioner/filter (which seems bizarre given the comparison of the technologies involved). Given that a DAC is basically just a small subset of what the Ultra does, I was not confident that a DAC would necessarily solve the noise problem, so your experience is very helpful, thank you.

just to be clear since i haven't detailed much in my last reply, my hum issue happened when i had connected RCA cable to the sub out - disconnecting the sub RCA and the hum (in the passive speakers) was completely gone. I already had SMSL SU1 DAC , and using it with optical out, appeared to solve my issue.
you wrote before that disconnecting the sub RCA improved the hum , but not completely

 

[dominikz]

I discovered while testing that if I touch the outer casing (top or side) of the Wiim with my hand the level of hum drops noticeably, to maybe half the volume. I have no idea what this tells us, maybe the capacitance of a human body is reducing ripple voltage?

This sounds to me like a ground connection is missing, so I'd second the advice from @jed1 to try and add a proper ground connection to the Ultra (e.g. via the phono ground connection).

Good luck!

 

[Steve Woodhouse]

Unfortunately I disposed of my last external DAC (a Cambridge Audio unit) some time ago, so this isn't something I can easily try.

High on the list of appeals of the Ultra were it's low cost and "everything in one neat box" tidiness. A return to a multi-device solution adds cost, and feels like a return to the big stack of stereo gear under the TV that this was supposed to replace.

Having said that, as I mentioned above, purely from a cost perspective an external DAC might be no more expensive than a mains conditioner/filter (which seems bizarre given the comparison of the technologies involved). Given that a DAC is basically just a small subset of what the Ultra does, I was not confident that a DAC would necessarily solve the noise problem, so your experience is very helpful, thank you.

I think you can pick up a cheap, transparent DAC with optical in for sub-£80; the SMSL PS200 is £76 at Amazon UK, the SMSL SU-1 is only £63.

Your initial problem has ground loop written all over it, and using a DAC with optical in as a bridge to eliminate this is a tried and tested method, with a very high success rate.

Ground loops have very little to do with the standard of the equipment. They can occur in any system where you have an chain of audio devices all plugged into the same mains circuit. It's really just pot luck.

 

[incans]

by any chance, do you have (any) DAC lying around, that you could test by connecting between the Ultra optical out to your monitor speakers?
i had a very similar issue with the Ultra, and by using its optical output instead of the RCA outputs, it solved my ground loop noise.

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?

 

[incans]

This sounds to me like a ground connection is missing, so I'd second the advice from @jed1 to try and add a proper ground connection to the Ultra (e.g. via the phono ground connection).

Good luck!

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?