6C45Pi

The 6C45Pi is a Russian single triode with extraordinarily high transconductance (~45 mA/V) and very low plate resistance, originally designed for wideband video amplifier and pulse circuit applications. It is one of the most linear small-signal triodes available, with distortion figures an order of magnitude lower than conventional audio tubes at typical operating points. The tube's extreme transconductance makes it challenging to stabilize; careless layout will result in parasitic oscillation, and it demands rigorous power supply decoupling and short signal paths. When properly implemented, it delivers a level of transparency and speed that approaches the best solid-state while retaining dimensional qualities unique to vacuum tubes.