EL34 and 6L6 tubes are not interchangeable without modification.
EL34 and 6L6 are both power tubes used in guitar amplifiers, but they have different electrical characteristics and pin configurations, which makes them incompatible with each other.
If you want to use one type of tube in place of the other, you will need to make changes to the amplifier’s circuitry, such as adjusting the bias, to ensure that the new tube operates correctly.
It’s recommended to consult with a qualified technician or amplifier specialist before making any modifications to your amplifier.
