So i use the Hi-power SS Rec mode only. My heater voltage was a little low measured @ Obeid Khans house. He said it was no problem but that this amp should only run on Diode Rec. What [if any] are the downsides of pulling the 5U4 Rec tubes ? Im theorizing that if i do pull then there will be more heater voltage to go around. This amp has a new quad of EL-34 now. Bias is spot on.