Hissing noise when using headphones

[RotatingNut]

Hi,

I'm relatively new to the PBP, having received it only a few days ago, and I have a problem:

Whenever I playback any video or audio on Firefox or Chromium and listen via my headphones I can hear a strange hissing noise that stops whenever I stop the playback. Also, in Firefox, the audio only plays back if the local volume setting (that is within e.g. the video player) is at its maximum. Am I doing something wrong?

I'd like to thank for your help in advance!

[drazurh]

I have the same issue, and it is not limited to playback using a web browser; I got the same noise when playing an mp3 using vlc.


Maybe there is some kind of interference with the DAC? Or maybe the DAC is just that bad. The hissing is pretty loud so it would surprise me if the DAC really is that bad. I don't want to resort to using a usb audio jack :-(

[drazurh]

I somewhat solved this for myself.

I don't think the DAC plays well with low impedance headphones. I was actually using earphones at first, which are very low impedance. I switched to using my he4xx planar magnetic headphones (high impedance) and the noise floor is low enough to barely be able to hear (you'd have to be in a very quiet room or really be listening for it)

The only potential issue with doing this is the DAC not being able to power the headphones enough. At max volume, the headphones are at about 60-70% my normal listening volume. I solved this by using alsamixer to change the gain of the DAC fairly higher. I haven't noticed any substantial distortion after doing this.

 I also tested some headphones with more average impedance (Audio Technica m50), and the noise is also fairly loud, but lower than the earphones.

Ideally, the gain of the DAC should be able to be lowered, but I can't find any way to do this. I think it's possible that the gain control in alsamixer only changes the output volume in software, and doesn't do anything to change the actual output power of the jack. Anyone that understands audio better let me know your thoughts on this.

For now, I guess I will stick to my planar magnetic :-p

[RotatingNut]

Thanks for the replies! I have noticed the same thing with the impedance as well. The "hissing" is clearly audible on my Major III, but when using my DT770 Pro headphones (which have considerably higher impedance) the hissing noise is low enough so that it cannot be heard. This is of course no ideal solution, as it is rather an inconvenience, but for now it works.

From a circuitry viewpoint, it might be a possibility that there's some sort of interference (the audio is being affected by the constant electrical signals on the board), which would go along with my initial observations that the hissing is most noticeable when the machine is under some considerable load (i.e. YouTube videos...). So maybe shielding could help with that, right?

Maybe there will be a nifty software solution to this...

[dlowe]

Thanks for the replies! I have noticed the same thing with the impedance as well. The "hissing" is clearly audible  on my Major III, but when using my DT770 Pro  headphones (which have considerably higher impedance) the hissing noise is low enough so that it cannot be heard. This is of course no ideal solution, as it is rather an inconvenience,  but for now it works.

From a circuitry viewpoint, it might be a  possibility that there's some sort of interference (the audio is being affected by the constant electrical signals on the board), which would go along with my initial observations that the hissing is most noticeable when the machine is under some considerable load (i.e. YouTube videos...). So maybe shielding could help  with that, right?

Maybe there will be a nifty software solution to this...

I got some traction on this!

1) From the command line, run pavucontrol

2) Click on the "Output Devices" tab.

3) Where it says port, change from "speaker" to "headphone"

That seems to be enough - the sound is much louder and more clear.