I have weird noise when I connect laptop headphones out to the usb audio card line in.
When I connect smartphone to this line in everything is fine. When I connect headphones to the laptop out everything is ok.

This noise appears on recordings.
This is an example:



I was similiar problem with noise when I connect Tascam recorder to the Akai sampler.
You can hear it on the beginning of this recording.

 

Last edited: Jun 7, 2020

That's barely audible. Could be a groundloop or problems with (too many) USB. Unplug devices (one by one, or add one by one) and see if the problem goes away/comes back.

 

headphones to line in? hum...

line in - is input. normal usage - send audio from other device to line in (for capture this audio with recording software/hardware, or send audio to amplifier, etc.)

headphones connecting to output. you won't hear anything in headphones after connection to line in.

why do you connect headphones to the line in?

 

You missunderstood. Read again. I connect headphones to laptop out.


When I was write laptop headphones out I mean this

 

Last edited: Jun 7, 2020

ok...
have you tried to disconnect power adapter from laptop and connect laptop headphones out to the usb audio card line in?

 

I checked laptop power adapter, all usb and them seems to be fine (nothing has changed). It looks like it's a ground loop problem with power extension cord.

 

Definitely a Grounding issue. Pick a different power outlet from the wall for whichever device the audio signal comes out of.

And what are laptop headphones supposed to be? I know headphones and I know laptop speakers…

 

Try it on a unground extension cord. Does the sound stay? If it dissappears, you have a groundloop.

 

Cause of the problem is Behringer HA400 Amp. I have SoundBlaster Xi-Fi 5.1 soundcard connected to HA400 input then 3 jacks output. First for speakers, second for sub, third for headphones. When volume knob is turned more than 1/4 this pitched noise is louder and is probably there all the time but much quieter so when I record something and then use compressor this noise can be clearly heard and 1/4 is not loud enough for me. I prefer 2/4 for listening. I don't know yet how to solve it. Maybe VB-Audio Virtual Cable? Or substitute for HA400?

 

REd Light : it is an Optical Output too
https://www.amazon.de/FosPower-Opti...t=&hvlocphy=1004273&hvtargid=pla-312488743612

use otical out