[Mikremk] demonstrates this with a simple but effective amplifier using a PCL82 triode-pentode. It’s a conventional tube amplifier circuit in which the triode is a preamplifier for the pentode ...
“By replacing the board you essentially change the entire circuit design, and it gives you the ability to use different driver tubes than the original, difficult-to-find 7199 triode/pentode. “The ST70 ...
The only part left was the discharge transistor; a pentode was enlisted to stand in for that vital function, making the circuit complete. To physically implement the design, [David] built a large ...