possible audio regression for usb-audio with 5.3 kernel (5.3.1), sounds like variants of 8-bit audio

[Matt]

Hi Takashi,

there appears to be a sound regression for plug-n-play usb-audio DACs
with 5.3 kernel.

I'm using the following one:

https://www.aliexpress.com/item/33012416525.html?spm=a2g0s.9042311.0.0.4f314c4dv3EF0p

which includes SA9023A + ES9018K2M on the chip.

When listening to parts of the Unreal Tournament 3 soundtrack the
output resembles a bit like:

https://www.youtube.com/watch?v=9gq4R6acnBQ Rush - Tom Sawyer (8-bit
NES audio render)

it immediately made me think of 8-bit audio and the NES.

First thought of misconfiguration in the kernel config but then went
back to 5.2.17-rt9 (copying the config and only enabling full
preemption) and there the output is correct and crystal clear.

For each kernel build I need to jump through a few hoops (nvidia
driver, zfsonlinux modules, luks, genkernel, etc.) so it'll take a
while to build and get it up and running.

System is:
cat /etc/lsb-release
DISTRIB_ID="Gentoo"

~amd64

gcc version 9.2.0 (Gentoo Hardened 9.2.0-r1 p2)
GNU ld (Gentoo 2.32 p2) 2.32.0

PCIe related sound doesn't seem to be affected (Xonar DX), it works
fine both on 5.3.1 and 5.2.17-rt9

Kind Regards

Matthew