Sound distortion with displayport connection

[kyrcy]

For a new monitor/graphics card setup with speakers connected to the monitor with displayport I occasionally hear distorted sound when watching videos online, playing multimedia files etc. Speakers work fine when connected directly to the PC. I am using the latest drivers available. Any ideas what might be the problem?

[Cornucopia]

The monitor/speakers?

DP is just a fast, high quality pipeline.

Try another (known-good) DP output to compare.

Scott

[kyrcy]

Speakers, as I wrote above, work fine when connected directly to the PC. If displayport is "just a fast, high quality pipeline" why should the monitor be the problem? I don't have a second displayport output to test, but same problem happens with hdmi too.

[Krispy Kritter]

The monitor.

HDMI and DP are both digital outputs. Speakers use an analog signal. So the digital feed into the monitor is being converted into an analog output for the speakers. Also, I've not seen a monitor with an amplifier circuit to drive speakers (unless you have self powered speakers). Analog outputs on monitors are typically designed for headphone use.

In any case, it's not the digital (DP or HDMI) output, it's the DAC in the monitor which is the problem.

[kyrcy]

These are the results from further testing:

1) I hear the sound distortion with new monitor/graphics card using displayport.

2) I hear the sound distortion either with speakers (self-powered USB) or with headphones connected to the new monitor.

3) I hear the sound distortion with an old monitor connected to the new graphics card using HDMI.

4) I don't hear the sound distortion with a different device (external DVB-T tuner) connected to the new monitor using HDMI.

5) I don't hear the sound distortion with onboard graphics instead of the new graphics card and the new monitor using HDMI.

[kyrcy]

Based on the above results do you agree that the problem appears to be the graphics card and not the new monitor?

I am using the latest drivers so I am assuming this is not a software issue, but could the problem be interference from the PC case?

[themaster1]

ground loop see here maybe or bad shielding (bad cable)