I've been putting some hours on my new TSE 300B amp to break in the Psvane Treasure MKII 300B's. My power transformer is an Edcor XPWR131-120. It has 660 volts, center taped. I have an 8.2uf cap in C4 position. When I power up the amp my B+ is 374 to 375 volts. As it warms up the B+ drops. It seems to stay around 370 volts for a while, then continues to drift down. After about 5 hours it has dropped to about 366 to 367 volts. Today, I turned it on, and B+ was 380 volt. After an hour it is now down to 375 volts. It's all within a decent range. So I'm not worried about ruining anything. I am just curious if this is normal with a new amp where everything is breaking in. Oh, I have about 71 hours on the amp now, and about 55 hours on the new tubes. Oh, the 300B's bias current drifts down as they warm up also. Although they are drifting less as they get more hours on them.Thanks all for all your help.