Re: JMP Bias weirdness, Losing ma's after "8" or "9" on Master!?
First of all, what are you measuring bias with? If you were measuring cathode current with an ammeter is series (like some bias probes do, that I personally would not use), what you could be seeing (and hearing) is your meter ****ing things up, since your meter COULD be going out of range.
What is the maximum range of your multimeter when set to the milliamps scale?
Really WASN'T a very good idea to be measuring the bias whilst cranking the amp unless you have a VERY good understanding of what you are doing and what your equipment can handle.
The other thing that concerns me, is 49 mA at idle (whilst allowing an extra 5mA for screen current) is really pushing your luck with modern EL34's, and although I disagree that 70% is this magical limit that everybody talks about, it probably should be adhered to for modern tubes, which just can't take the punishment of my old Tesla's, Mullards and RFT's can handle. At 49mA you have gone over that 70% slightly, and I'd back it down a little, unless using decent tubes from the early 70's or before.
Sorry if this sounds a little harsh, but it wasn't the most intelligent thing to have done. If the meter did crap out on you, then your cathode ground would have been seriously compromised and unnecessary damage may well have occurred.