Noise on Subwoofer Output

[slartibartfast]

I saw some early tests where it was mentioned that there was high frequency noise on the Subwoofer output. My Subwoofer has a switch to bypass the inbuilt low pass filter which would be the preferred option when using the bass management of the WiiM Amp. Problem is I can hear output when nothing is playing with the switch in that position. This noise disappears when I switch the low pass filter back in.

 

[harkpabst]

Yes, this could potentially be an issue due to flaws in the first hardware revision or early manufacturing (it could also be something else).

Do you know the PCB version of your amp or how to retrieve it? Get your amp's IP address (from the WiiM Home app network settings page or your router's setup) and replace the xxx values in the following link with the actual IP address. Then copy this link to your web browser's address bar (phone or computer, it doesn't matter). You will probably be informed of an invalid TLS certificate, but you can safely ignore this warning and continue. The result will be a very long string (text in JSON). Search this text for the value following the key "PCB_version".

https://xxx.xxx.xxx.xxx/httpapi.asp?command=getStatusEx

Bypassing the internal filter of the sub would be the preferred option, indeed. Many subwoofers feature another lowpass filter high above the intended pass band (e.g. anywhere from 500 to 1000 Hz, that cannot be switched off, but some may not (or it might be to high to help with the noise).

 

[slartibartfast]

Yes, this could potentially be an issue due to flaws in the first hardware revision or early manufacturing (it could also be something else).

Do you know the PCB version of your amp or how to retrieve it? Get your amp's IP address (from the WiiM Home app network settings page or your router's setup) and replace the xxx values in the following link with the actual IP address. Then copy this link to your web browser's address bar (phone or computer, it doesn't matter). You will probably be informed of an invalid TLS certificate, but you can safely ignore this warning and continue. The result will be a very long string (text in JSON). Search this text for the value following the key "PCB_version".

https://xxx.xxx.xxx.xxx/httpapi.asp?command=getStatusEx

Bypassing the internal filter of the sub would be the preferred option, indeed. Many subwoofers feature another lowpass filter high above the intended pass band (e.g. anywhere from 500 to 1000 Hz, that cannot be switched off, but some may not (or it might be to high to help with the noise).

Mine is PCB version 5 which is why I was surprised. Maybe it was worse with the early PCBs. It doesn't appear to be particularly high frequency either. By reducing the gain of the Subwoofer and boosting the Subwoofer output of the amp I can virtually eliminate it.

 

[harkpabst]

By reducing the gain of the Subwoofer and boosting the Subwoofer output of the amp I can virtually eliminate it.

In that case it's almost certainly noise generated by the sub's amplifier itself!

But that's OK. Finding the optimum gain structure of sub and amp is crucial, but too rarely mentioned. I recommend to start with the sub's volume knob at ~50% and adjust the final level in the amp's settings (which is far more accurate).

There's nothing wrong with maxing out the amp's subwoofer volume setting, as long as it leads to further improvement. At some point it might swing back, though. Simply go with what's working for you.

Good to see you've been solving your own problem.

 

[slartibartfast]

In that case it's almost certainly noise generated by the sub's amplifier itself!

But that's OK. Finding the optimum gain structure of sub and amp is crucial, but too rarely mentioned. I recommend to start with the sub's volume knob at ~50% and adjust the final level in the amp's settings (which is far more accurate).

There's nothing wrong with maxing out the amp's subwoofer volume setting, as long as it leads to further improvement. At some point it might swing back, though. Simply go with what's working for you.

Good to see you've been solving your own problem.

I don't hear the noise when the sub isn't connected to the WiiM sub out even at maximum gain so it doesn't appear to be caused by the sub itself. I did start with the sub gain at 12 o'clock which is often recommended for the phono input of the BK XLS200. I dropped it back slightly then added 3dB in the WiiM app.

 

[harkpabst]

I don't hear the noise when the sub isn't connected to the WiiM sub out even at maximum gain so it doesn't appear to be caused by the sub itself. I did start with the sub gain at 12 o'clock which is often recommended for the phono input of the BK XLS200. I dropped it back slightly then added 3dB in the WiiM app.

I did have noise issues with my pair of XLS200 and if I remember right, different subwoofer cables and connecting everything to the same power outlet did help to minimise the effect. Could well be stray noise.

 

[slartibartfast]

I did have noise issues with my pair of XLS200 and if I remember right, different subwoofer cables and connecting everything to the same power outlet did help to minimise the effect. Could well be stray noise.

I think you've hit the mail on the head. I left the cable plugged into the subwoofer and disconnected at the amp end and heard similar noise. Connecting a different cable was fine. However connecting the new cable to the amp and turning the gain to max on the subwoofer revealed a quieter regular pulsing sound. So there is something there just nowhere near as bad as I first thought.

 

[bherren]

I don't hear the noise when the sub isn't connected to the WiiM sub out even at maximum gain so it doesn't appear to be caused by the sub itself. I did start with the sub gain at 12 o'clock which is often recommended for the phono input of the BK XLS200. I dropped it back slightly then added 3dB in the WiiM app.

Could be a ground loop, try using a different power outlet for example

 

[harkpabst]

Still nothing wrong with upping the level in WiiM subwoofer output and reducing gain on the BKelec, if it helps to minimise the noise.

Good to hear things have worked out.

 

[landco]

bkelec is the same as REL, the same level of quality:

so it's quite possible that the subwoofer is to blame and not the amplifier

 

[harkpabst]

I think that price and value are very much different, aren't they?

 

[jed1]

Perhaps, unbalanced cable picks up RF, EMI, ground loop, washing machine, aquarium pump, and etc.?