How to build your own tube amplifier?

Your best bet is to first build a time machine and go back to about 1955, when we had Dyna Kit, Eico, and Heathkit, among others. There are outfits today that make and sell tube amp kits. Check this out through Google.

http://audionotekits.espyderweb.net/price.html
I didn't try it, but it looks interesting.

You don't need to go back to 1955?? Go today, to diyaudio. They have a whole section devoted to DIY tubes. Read this for a few weeks, and you will be full of ideas. Just look at the thread subjects!!

http://www.diyaudio.com/forums/forumdisplay.php?forumid=5

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