Is it possible and safe to connect my electric guitar to XLR input in my Focusrite - Scarlett Solo?
If so, will I be getting worse signal from XLR than instrument input ?
Assuming you don't have some kind of Franken-cable running from ¼" jack to male XLR, then you'd have to go via a DI [Direct Injection] box, if only because the plugs won't fit otherwise.
If you do have a Franken-cable, throw it away.
Impedance mis-match, wrong signal voltage levels & the potential to return 48v back to the guitar are 3 of the best reasons to not do it.
A DI box solution would be perfectly acceptable, as it would eliminate the 3 reasons.
No. If you plug your guitar chord into a direct box, you can go out the XLR outee and into an XLR input. It will actually balance your signal and make the high end frequencies sound more harmonious. My acoustic has a built in amp and an XLR output; it sounds awesome. You just need to make sure that if you are plugging into a mic input that there is NO PHANTOM POWER. In fact I wouldn't even do that if it's a phantom power XLR jack since at some point you might forget it's on and plug in anyways.<<--That would send 48V of electricity up your XLR cable and into your guitar. Make sure f there is a 48V switch that it is off