You know, I thought a tube used in a computer sound card would be just crazy enough, so I googled it. You can get one for your desktop.If your laptop uses vacuum tubes in its output that feed a matching transformer then it needs a load.
Plan on running audio output from laptop into high impedence amp input. Do I need to add a 10-20 ohm resistor to the laptop output to represent the normal earphone/speaker load?
Or is it ok to run directly into high impedence input?