Linux ALSA - crackling sound on input

Hi, I’m running Renoise on Ubuntu with a USB soundcard (Focusrite Scarlett 2i4) and ALSA.
The output works fine but any time I try recording my keyboard using the input device, the sound is crackling (even using realtime priority and trying all the settings).
The thing is, when I run Audacity and record my keyboard with the same ALSA parameters, the sound is normal.

Any idea how this could be fixed ? (I’d like to avoid using Jack)

Crackling on input usually means the software cannot process the audio as quick as it gets in.
Raising the audio buffers is the only other solution here.
Audacity is using less cpu resources because it is doing a lot less than Renoise in the background.

Thanks for your response.

I hadnt’t thought of cpu but I’m wondering if it can be about it, as CPU usage doesn’t go over 2% while recording.
Raising the buffers does improve the recording a little bit, but it still doesn’t work properly.

The weird thing is, I’ve tried with Jack and recording works just fine.
But I find Jack annoying + it creates other problems (for example, wrong speed when opening some songs)

Anyways, let me know if anyone has an idea.
If I find out, I’ll post about it here.