Audio Express Magazine has published an article that i wrote on a portable tube preamplifier. This preamp was developed so that we could record live concerts with high fidelity. The hard part was to use tubes for this (or any) portable application. If you find this interesting, please read on by checking out Audio Express Magazine online.
If you find audio projects to be interesting then support this community by buying a subscription to Audio Express, it is a fascinating magazine with numerous makers building audio projects including; amplifiers, preamps, solid state amplifiers, tube amplifiers, speakers, and etc. I plan to contribute with more articles in the future, if you have anything interesting that you have built i'm sure they would want to hear about it :)