2 Guitars in 1 Input// SOUND PROBLEM

Hey guys,

here's what I'm trying to do:

I want to run 2 Guitars at the same time, so I can play my acoustic, loop some chords, grab the electric (Fender Strat) and play a solo.
I bought a Y-Cable Adapter so both guitars are plugged into the adapter and the adapter itself runs into the Kemper Front Input.

Problem: The acoustic sounds is changed by the Strat. When the volume at the Strat is off, the acoustic is, too. And as soon as the Strat is plugged in the acoustic sounds a lot thinner and not as full.
Is there any way I can fix this?
I didn't want to go with a ABY Box and was hoping that the Y-Adapter was the perfect and easiest solution.

Please help !
And thanks in advance...