Hi all I've had my SP9 Intel version for just 3 and a half years now and not had any issues apart from the well documented audio popping issues right from the start. Firmware updates over time have made gradual improvements and when running from an external battery using type-C there is no audio popping now. Its a major issue for me as I use a screen reader. The popping only occurs when running from the internal battery.
I've been tinkering in the registry to enable all the hidden power settings and I've found if you disable CPU idle states the audio popping completely disappears but you take a massive hit with battery life.
The audio popping is really bad on battery on Windows 11 25H2 but its a lot better on the latest Canary build but its still there.
I found a much simpler fix by accident yesterday go to control panel, power, click your active power plan which should be balanced in most cases, click change advanced settings and scroll down to PCI express, expand link state power management and select "off" on battery and on AC. Click okay and job done no more random audio pops on battery and battery life is still excellent.
To test the audio play a high quality live stream such as any of the BBC channels on Iplayer. Usually the pops would occur every few seconds but after disabling PCI express link state power management audio is rock solid and stable even when putting the SP9 under load such as when generating UUP iso images.
Naturally I'm running the latest SP9 driver package and firmware so everything is up to date on the software side.
Please comment if this works on other Surface models.
I should make it clear I have no idea what disabling the PCI express link state management setting does on other hardware especially if you are running an EGPU etc but for a basic setup this method works 100%.
Hope this helps others out there.