[SOLVED] hisssssssss in the background

[hapibeli]

SOLVED

[bluebell]

I have a new install of Ubuntustudio on my 2 year old Lenovo T440S , but still have the same background hiss as I do on my older Lenovo T430 with Kubuntu and KXstudio.
They are both using my new Behringer UMC404HD usb interface. If I run directly from the Behringer into my mixer from the keyboards and/or mic, the sound is clean. Tweaking the Behringer gains helps clean it as it comes from the laptop, but,
is there a way to clean a laptop's signal?
I am assuming that the laptops are adding dirt to the mix? If so, is there a way to clean it up?
I use Reaper and/or Audacity.
Thanks all.

Do you have 2 devices connected (e.g. computer, keyboard, mixer, amplifier) where each one has a grounded power connector? Then you might have a ground loop. This can result in hum but also in hiss, sometimes influenced when moving the mouse.

Use only devices with balanced cabling, make unbalanced outputs balanced with a DI box

[andersen]

Hi B,

Check plugs. Common source. (wiggle to ensure they are properly seated) Also, bypass the mixer to see if it's responsible.
Are impedences matched(affects gain). That leaves two things: gain, or another piece of equipment - including cables (and plugs).

Good luck