Audio from Notebook: Noise via VGA port

2010-11-24 10:21:44

I have a Thinkpad T23 with a SB Audigy 2 ZS Notebook - attached via VGA to my Television. Everything seemed to be solved, but the connection to my television emits some slightly audible mid/high frequency noise, which annoys me. First I was thinking about some CPU power management problems, but no success here, I did BIOS updates etc... Turning VGA off via FN+F7 also doesn't help...

- Remove VGA connection on Notebook or TV side: Noise removed

- Turn Television off or EVEN UNPLUG it from AC: Noise remains.

The notebook has no DVI, so there's no other solution than using the VGA port (I want to use my television).

What can I do? I need your input, before I start buying other soundcards (echo indigo e.g.) and maybe being not successful then. Would I have no problems with using USB (the T23 has two slow USB 1 ports).

TIA

Audio from Notebook: Noise via VGA port

Reply #1 – 2010-11-24 20:52:02

I recommend you do some searches on the subject. Many notebooks put noise into the audio because of their power supply design. Most often the noise is not generated when using battery only power. It generally doesn’t matter what type or brand of audio interface is in use. There are a variety of possible cures, none of which work with all notebooks. Some notebooks seem to have no solution beyond the major surgery of replacing the power supply with a different kind.

One possible solution are a ground lifting interface at the mains power plug. I know people have reported a number of others. I also remember reading about an external mains supplied power supply that essentially runs the notebook through its battery, bypassing its built-in power supply, but is itself plugged into the mains. I don’t know who sells it.

Audio from Notebook: Noise via VGA port

Reply #2 – 2010-11-25 05:05:52

I did search, but I was on the wrong path...

Pulled the plug and... Silence  I'm very thankful for your posting, it's the exact reason for my problem!  I'LL see if I find something for my Thinkpad T23.

Audio from Notebook: Noise via VGA port

Reply #3 – 2010-11-25 10:03:37

Similar problem on my ViewSonic monitor on the PC using DVI-digital video but analog audio so I can use a plain pot to control the audio rather than showing the wife and kids how to use the menu settings for volume. The previous monitor had no issue but the new one did. For this I 'loosened' the audio ground connection by adding a 10 ohm resistor in series with the ground. The ground loop currents are now reduced and not causing problems any more.

G²

Audio from Notebook: Noise via VGA port

Reply #4 – 2010-11-25 13:59:07

Hmm, are you hearing some kind of "cpu or bus working" noises? Morsecode, ticking things? For testing purposes, I removed connection to ground, but no success, noise remains unfortunately.
Maybe this: http://www.thomann.de/gb/palmer_pli03.htm would help me, but I think putting some kind of filter into the audio chain is the wrong way to go.