I recently installed Kubuntu 20.04 on a new Razer Blade 15 (mid-2021) with built-in audio card Realtek ALC298. Everything has been working pretty well audio-wise, with PulseAudio working perfectly fine.

I recently installed SuperCollider and Reaper, two pieces of audio software that require JACK to run. I've installed JACK via the Ubuntu Studio packages. Now, however, whenever I boot the JACK server my audio becomes severely distorted, a bit like clipping distortion.

This seems to be the case with any audio coming from SuperCollider and Reaper. But also other applications, such as various software synthesizers. Even the volume control system sound starts to distort horribly above a certain level.

Does anyone have any idea what might be the issue? I've tried both generic and low-latency kernels.. (5.11.0)

thanks!

EDIT: This issue does not occur when using an external (USB) soundcard, in my case a Behringer UMC204HD. It seems to only be an issue with the ALC298 built-in audio.