Just a quick follow up, it’s been a few days since I’ve removed the output muting transistors and my sound card has been working great. I’m not planning to replace the transistors but I dug around for some information as to what they are.
The original removed parts are in a SOT-23 package, marked MAX on top with 2 small numbers (33) going the other way, which I later found out to be the lot nunmber.
led me to this part number KTD1304 and datasheet
It’s manufactured by KEC in Korea, which sounds about right given Auzentech is a Korean company, I hoever can’t find this part stocked on the usual suspects (Digikey/RS Components/Element 14).
I did find some sellers listing it on Ebay though, so that might be an alternative if I ever want to get them changed out.
Electroschematics has a great article as well as an excel spreadsheet of some of the other available specialized transistors suitable for audio muting.