Hello!

I got a Scarlett Solo 3rd gen, and I'm trying to have it set up to my PC, however I'm encountering an issue.

This is my setup:
Guitar -> Interface -> Line in PC (through jack cables)

The PC has a high quality onboard audio codec (Realtek ALC1220). However I'm getting horrible static from this configuration.

Guitar directly to line in is CRYSTAL CLEAR (perceived through listen mode in control panel).

Guitar to interface is also CRYSTAL CLEAR (perceived through listen mode also).

Only when connecting the interface to the line in PC, whatever output of the interface I use (headphones or R/L) the static tone appears.

Why is that?

Thank you!

Is it static (ground loop) or feedback?
Why would you connect it the way you are doing?
Use the USB.

Like BT said. You shouldn't be connecting it that way. Run whatever you are recording (mic, Guitar DI, etc.) into the Scarlett and connect that via the USB out to one of your computer's USB ports. Make sure you download and install the latest Focusrite drivers for your interface.

Hmmmm...I think that with more experience, you'll find that the words "onboard audio codec", "Realtek" and "high quality" don't usually belong anywhere near one another. It's highly likely that connecting the Scarlett via USB and letting it handle all the audio duties will not only work far better than trying to connect its output to your computer's line input, but also give you significantly better audio quality than any codec you'll find on a PC motherboard.

Onboard audio codecs are generally chosen by computer manufacturers on the basis of:

1. Low cost
2. Simplicity of use (from the point of view of the motherboard designer/computer manufacturer)
3. Familiarity.

At best, audio quality probably comes a poor 4th to the above. If it even makes the list at all.

An external audio interface - even a cheap one - will typically use a better quality ADC/DAC, have better ancillary electronics, have better analog circuitry and have a better overall design from the audio pathway point of view.

So...while it may be true that the ALC1220 is a "high quality" codec compared to some other onboard audio devices, that's basically just saying that it's slightly less crap than a bunch of other things that are very crap indeed. You don't tend to find any of the onboard codecs (Realtek or otherwise) being used in professional audio equipment or even in cheap and cheerful audio interfaces. There are reasons for that...

General rule is that when you buy a dedicated sound card, you disable the on-board sound card and never use it. Because the on-board sound chip it very cheap, doesn't have as good as driers as a dedicated sound card and doesn't have good circuitry either.

Why have your dedicated sound card go through the PC's built in sound chip? Disable it and bypass it and never look at that thing again