TOPIC:

Hello!

I´ve made an subwoofer using this plate amplifier. Everything works otherwise fine, but I just noticed that my HTPC causes noise and rumble that comes out from my subwoofer. With other sources (Squeezebox, PS3, PVR) there´s not any noise. I´ve just checked that cables from my HTPC and RCA-cable between my AVR and my subwoofer don´t go near each other, and tried also to move my HTPC further from my subwoofer. Rumble and noise still comes out from subwoofer when ever there´s some sound coming out from my HTPC. Noise volume is always the same, so it´s not related to my AVR´s volume.

My gear is Onkyo TX-NR818 and Intel NUC HTPC. What can I do? I had a normal NAD power amplifier as my subwoofer amplifier, and there wasn´t any noise problem with it.

And problem solved... Finally I tried to turn HTPC´s power plug around and that helped.

I hope this helps someone with same kind of problem.

Problem still persists, noise now lower, but still there. I´ve moved PC´s PSU as far as possible from subwoofer and tried also to move HTPC further, but it didn´t help.

On other sources PWR-ICE´s input level shows between -75-80db when muted, with HTPC it shows about 65db and this noise can be heard clearly through subwoofer.

Any ideas what to try next?

Depending on where you live, try the right version of this: www.amazon.co.uk/Supra-LoRad-6-Way-Distr...r=1-1&keywords=supra
I got rid of some power related noise, probably generated in one or several switched powersupply(s). You can also try to turn the powerplugs one by one on the rest of equipment. If you have a multimeter, you can measure the voltage between the cabinet of the different components, should be as low as possible.

@ juukeli
PC sources depending on the sound card and grounding/earthing can be troublesome at times. Can you clarify if your PC is earthed correctly?

Are you using an analog source here from your PC to the PWR-ICE? If you are, one thing you could try is to add an isolation transformer. Do you happen to know if the noise is around 50~60Hz (ground loop). Google ground loop for some examples of troubleshooting.

DevTeam

My PC is Intel NUC minipc, model is dc3217iye. The PSU power plug has got grounding pinds normally and it´s connected to grounded extension wire which is connected to grounded wall socket. Sound comes out from hdmi-connection to my AVR. The noise comes out only when there´s sound output from PC, if PC sound is muted, noise stops. Muting AVR doesn´t stop the noise.

I have also another power amplifier connected to my AVR, and there´s no noise coming through speakers it´s driving. There´s also no noise on speakers that are directly connected to AVR.

Just tested with other PC (Zotac ZBOX ID33BR), and there´s no noise with it. I´ll have to find out wether PSU´s are compatible between these too, and test NUC with ZBOX´s PSU to find out wether it´s the NUC´s PSU that causes this problem.

Interesting. As mentioned before the most likely is a ground loop. That's why you'd hear a "rumble" sound.. Our guess is down to the enclosure grounding on the PC. A lot of times it's not properly earthed. You could try with a ground earth to the case OR just try to isolate the ground loop (google ground loop isolator)

DevTeam

I don´t think it´s ground loop because noise disappears if I mute sound from PC. And it´s impossible to ground the case because it´s made of plastic.

How can I use ground loop isolator with hdmi -connection?

juukeli wrote:

I don´t think it´s ground loop because noise disappears if I mute sound from PC. And it´s impossible to ground the case because it´s made of plastic.

How can I use ground loop isolator with hdmi -connection?

There must be a place one the rear of the PCB or the corner of the PCB that should be grounded/earthed.
As for the HDMI question, no idea how that's relevant to the PWR-ICE since these don't have HDMI input..

Just to confirm, you're going Analog OUT from your PC to Analog IN to the PWR-ICE .Right?
If so, that's where you need to isolate your ground we'd guess. Our 2cts.

Devteam