So I'm waiting on the last of the parts to build one of these. I'm doing a few little tweaks to the original circuit, nothing major, just stuff like adding an adjustable bias, and using a switching pot for the presence to have the option of defeating the NFB loop by 'clicking' the presence control all the way left. The other thing I want to do is to do something about the dubious screen grid situation on the power tubes. As you can see, there are no screen resistors, and the screens are connected to the B+ voltage, so they would probably have nominally the same potential as the plates, which would not be good for tube life. So what I want to do is move the plate supply to the spot between the first filter and the choke, and leave the screens where they are, after the choke. Sorta like on a 5F6-A bassman. I also was planning on fitting 470Ω screen resistors (I've got both big 2 watt carbon comps or 5w wirewounds laying around). My questions are: 1) will the screen resistors change the sound? I've heard varying opinions on this. I assume 470Ω is the appropriate value, but some people like to go lower and others like to go higher. 2) Since I'm moving the B+ supply to a spot before the filter choke, should I up the value of the first filter cap to, say, 30µf? Or will it even make any difference to have the B+ before the choke? I notice the 5F6-A has two 20µf in parallel before the choke, while the 5E6 is configured like a 5E7 with a single 16µf on either side of the choke and the screens/plates tied together and connected after the choke. What do you recommend I do here? 3) Is there anything else I should be considering with this little tweak? Thanks to anyone who can respond. It would be especially great if someone knowledgeable like Aiken (made you look! haha) could respond. Thanks.