Finished my headphone tube amplifier!
From the tests, it looked like the amp was working correctly.
When I tested it, it actually was working, although I noticed that I had the volume control reversed so I had to rewire the volume control pot because it was becoming quieter when turned clockwise instead of louder.
After fixing that and doing a quite left right channel test to make sure I wired it correctly, I earthed the case by soldering a wire to ground the case and closed it up.
The amplifier is complete! I used a DIY 12v power supply to power it. I built the 12V power supply using a transformer to bring 240VAC down to something like 15VAC which I used some diodes to rectify to DC voltage and regulate down to 12V DC. For the power supply, I based it of a simple schematic I found attached to an eBay auction for a cheap power supply kit and etched my own circuit board. It has fuses connected as well in case there are any shorts for safety.
The tube is actually quite nice sounding and although it has a bit of background noise, it is about half that of some of my previous tube amplifiers. I might consider using this at work as my dedicated work headphone amp as it’s quite eye catching.