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.
Agreed. I bought 45 6N8S tubes for ~$100 CAD 6 or 7 years ago. They are about $5 US each now. Luckily for me, few people praise the 6N3P and they are still affordable. Even 6F12P is getting hard to find and expensive.