[LAU] Scarlett 3rd gen glitches (again) + Raspi 4

[Iain Mott]

Hi list,

I have a Focusrite Scarlett 3rd Gen interface that is producing audio 
glitches with a Raspberry Pi 4 running a realtime kernel (or not). I had 
similar problems on a laptop and on a desktop. On the laptop however it 
now runs perfectly with the very latest Linux Mint and the standard 
kernel. On my desktop I get acceptable results with AV Linux although 
haven't tried it with the latest Mint. There are no error messages 
reported or overruns, just glitches which are independent of buffer 
sizes and sample rates.

The kernel installation procedure that I used for the Pi 4 is here:

https://lemariva.com/blog/2019/09/raspberry-pi-4b-preempt-rt-kernel-419y-performance-test

and the actual kernel that I built is: 4.19.71-rt24-v7l+

Can suggest some things to try?

Thanks a lot.

Iain