It was quite easy actually, but I take no responsibility if something goes wrong! Lol
1. Pull amp tray
2. Pull as many preamp tubes as needed to get at the stock fan's two screws
3. Unscrew the stock fan
4. Cut the two wires (red and black) fairly close to the stock fan
5. Strip ends of the the red and black wires coming out of the amp so about 1/8 to 1/4" of bare wire is exposed
6. Cut the connector off of the Noctua fan leaving plenty of wire coming out of the fan
7. Strip the yellow black wires so about 1/8 to 1/4" of bare wire is exposed
8. Connect the red wire from the amp to the yellow wire from the fan; connect the black wire from the amp to the black wire from the fan (I used Wago connectors because I was being lazy; you can just solder them)
9. Put the preamp tubes back in (not sure this is needed yet)
10. Turn on the amp to test that the fan comes on
11. If fan is operational, reassemble and enjoy the silence
THIS is the fan I used