Having managed to build the 5F1, with a lot of help from people here, I feel like I've got some kind of understanding of what's happening in most of the circuit. One thing that I've been wondering about is what's going on with the cathode resistors on V1. Can someone explain to me where the 1.5DC is coming from on Pins 3 and 8 of the 12AX7? My understanding is that the filaments heat up the cathodes which gives them a negative charge? Would I be right in saying that the cathode resistor acts like a valve to dump some of that charge to ground in order to get the right level of negative charge on the cathodes? Or am I way off? Thanks again!