[JRace]

I am using a Buttkicker class D BK1000 amplifier to drive a DIY sub.

I have a laptop in my audio chain and whenever it is plugged into AC there is a very audible anoying HUMMMM from the sub amp.

The sound goes away only if I do one of the following:
Disconect the AC power to the laptop,
or
Disconect the vga out from either the projector end or the laptop end.

Any ideas?

The hum is present even without CATV connected.

My signal chain is:

Laptop:
- VGA to projector
- Optical SPDIF to receiver (tried onboard optical SPDIF, onboard analog , outboard usb optical and coax)

Receiver out o sub:
- LFE/Sub 100Hz to BK1000 subwoofer amplifier via analog RCA

Thanks for any help....

[Wayner]

This is a common problem with laptops. If you fool around with what is on your screen, you might find that the more intense the image, the more pronounced the "hum". What this is caused from is poor video shielding and is being picked up by the sound card.

The cure is a USB d/a converter to get the analoge as far away from the video as possible. This is also not always successful. Good luck on this one. May also be weird ground loop.

Wayner

[JRace]

Hmmm....
I turned off the Screen and the hum went away.
If I lower the brightness it actually sounds louder.

And I think I found another source of the problem, removing the DVI-HDMI cable from the chain will get rid of the hum.

Doesn't surprise me...it is 35' long and has no chokes...

[Wayner]

So your good to go, for now?

[JRace]

Well...I can live with it for now.

Thanks for the info.