Hi, Has anyone built an amplifier with a gu-84b tetrode? In the datasheet the maximum anode voltage is 2.2kilovolt, but I've found a few websites where they apply 3.5 to 4 kilovolt. I wonder if this is a good idea, and if the life time of the tube is changed with this higher voltage. Who has experience ? best regards, Jan , ON6ZG www.on6zg.be