[LAU] Realtek ALC882D

[Sampo Savolainen]

On Wed, 2007-07-25 at 08:15 -0700, Ken Restivo wrote:
> It's a laptop.
> 
> We're talking about 19VDC here. IANAEE, but I imagine that the $20 laptop power supply will sacrifice its life in case of lightning strike, horrible mains power fault, surge, or other disaster, leaving both the laptop and the performer intact.

Don't fool yourself. The power supply uses 115V AC or 230V AC depending
on your area. When a design is meant for grounding, there is usually a
common ground point where everything in the device is connected to. If
you disconnect the ground, a short between any ground point and the
mains voltage will flow to your laptop through the "common" (0V) pin of
your PSU. This will eliminate any buzz from the laptop permanently, but
only after it stops sizzling.

The PSU has been designed to be be grounded, hence the ground pin. 

> Up until this year, I've never seen a laptop power supply with a ground pin anyway, at least here in the USA. They've all been two-pin AC, no ground. I've never had any kind of dangerous problem with them, in nearly over 15 years of using laptops. The grounding of laptop power supplies is a new thing.
> 
> Finally, I always run all my stuff off of a multi-outlet strip with a breaker. That thing is supposed to give its life as well too. 
> 
> There is no other solution. I've been told that the buzz/ground problem is *inside* the laptop and all of them have it. It's a cost-saving and space-saving measure that the PCB designers make.

I'm sorry, but this just is not true. If the "buzz" would be *inside*
the laptop and couldn't be affected by things outside it, how would
removing the earth connection help?

To properly remove the hum, there are a large number of options. 
 - If you are using balanced connections, you can disconnect the ground
pin on the balanced connection from either side of the cable. 
 - There are isolation transformers which electrically separates the
input from the output.
 - You can separate the ground between the input and output using a very
small resistor and a capacitor in parallel.

> I also need to point out that changing audio interfaces did not eliminate or even mitigate the buzz, and, I'm told could not have done so. I heard the buzz with USB and firewire interfaces.

Which is natural as the USB or firewire device will be connected to the
same electrical system as the PSU. 

Please, for your own sake, fix the hum properly. And for everyone elses
sake please don't recommend removing the ground pin.


  Sampo