[kluszon]

I've got the problem with the sound quality on analog when the device's in analog video mode.

Kodi 16.1
OpenElec 7.0.1 

1. When I've got hdmi_force_hotplug=1 set, I've got good sound quality on HDMI and analog with and without HDMI device connected. With these settings, I can't play video over analog.
2. When I've got hdmi_force_hotplug=0 set, I've got good sound quality on HDMI and analog with HDMI device connected, but without HDMI in A/V mode sound stutters (audio_pwm_mode=2). When I change (audio_pwm_mode=3) sound doesn't stutter, but the quality is low...

Can I do something with it? I want to have a possibility to change video output from HDMI to analog video and have good sound quality with HDMI and analog V/A.

[Klojum]

The analog sound implementation on the Raspberry Pi is of lesser quality to begin with.
The amount of static noise with analog sound is clearly heard. The overall volume as well is not that great.

Kodi 16.1
OpenElec 7.0.1 

That is a setup of at least 4 years old. Kodi software has moved onwards, OpenELEC is no longer maintained.
You could try LibreELEC 9 but I have a feeling your problem is more hardware-related than software-related.

Can I do something with it? I want to have a possibility to change video output from HDMI to analog video and have good sound quality with HDMI and analog V/A.

You may have to bumped into the Mixing digital video and analog audio limitations of a $35 kid's toy.

[kluszon]

@Klojum Thank you for the answer. I'll check your suggestions.