WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
Building, troubleshooting and testing of these amplifiers should only be
performed by someone who is thoroughly familiar with
the safety precautions around high voltages.
I built the Hagerman Cornet2. The build was really straightforward and the amp sounds great. You will need to buy the parts yourself, but part numbers are listed, the instructions are clear and Jim Hagerman answers email questions promptly.
I changed the brand and value of the output caps, although the recommended values work extremely well and cost significantly less than the "boutique" caps that I have used - yes, I stepped on the slippery slope and slipped!