My Dad RIP, did that too. I had so many old tubes back in the day. Back to tone/safety of the amps...I would doubt highly anyone could hear the bias shift of 5VDC. The amp wants stable voltage and current but no way will what was posted blow a fuse or have cause for concern like a spike/fault ect. If something goes like a grid resistor or tube it was going to anyway and should that happen hopefully the fuse will catch it and protect the amp.