Gunsur, actually coupling caps are connected between tube plate and the next tube grid.
Most coupling caps are in the range range from 0.1 uF to 1 uF. Since the input gain tube and the driver tube usually run off a 300 to 400 V DC supply, 1200V Mundorf caps will do fine.
This tweak is for a qualified tech only, because the output tube (and many surrounding circuits) use very high voltages. My guesstimate is 800 to 1200 VDC, AKA lethal if touched.
Most coupling caps are in the range range from 0.1 uF to 1 uF. Since the input gain tube and the driver tube usually run off a 300 to 400 V DC supply, 1200V Mundorf caps will do fine.
This tweak is for a qualified tech only, because the output tube (and many surrounding circuits) use very high voltages. My guesstimate is 800 to 1200 VDC, AKA lethal if touched.