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.