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.
Here is a preamplifier "audiophile" based on triodes 6h30 Russian and in a configuration inspired by the Conrad Johnson ACT2 mono floor based on the fitting of two parallel tubes.