I like to relax with a hobby that can relax my mind and be a lesser challenge than my normal everyday life. So to take on something I find easy and comforting, I like to take on some technical build project. Lately I’ve repared an iMac, now I am building a small, battery-powered stereo amplifier that can be used with a good headset and a musical source such as a computer, MP3 player or a smartphone like iPhone or Android. And I am not just building a regular amplifier, mine will be a tube amp. Since most experts believe that a stereo with tubes instead of transistors will give better sound, I wanted vacuum tubes for my headphone amplifier. One showstopper of course when you think about it is that most vacuum tubes run at a very high voltage (400v) and require a lot of power. I got a hold of some military-spec really small ones that will run off a 9 volt battery for around 70 hours. (10mA load for the entire circuit). I can safely use batteries on this small set, and not worry about either heat or high voltages. And still get that expert sound that you read about in Hi-Fi magazines. But at the cost of only $30.