Hi FXR,
Glad you chimed back in ...I was kinda hoping you had the answer!
So in seems like you're saying YMMV, depending on a specific amp design? Is it the circuit's design that dictates how much the PI will draw? I am wondering if the higher mA spec on the AT7 is even a
relevant point to an amp's design in the PI spot (I know it
is in the reverb spot on Fenders, but the PI is a different animal altogether). Pehaps the current draw in the PI position doesn't even merit discussion as it's so low (below the threshold of an at7, that is) and we're all just pointing to a distinction without a net difference (in terms of mA actually passing through the tube). Again, I don't know, but sure would like to.
Your example of cam tuning (lift, duration, lobe centers, etc.) is not lost on me. It's all too easy for a numbnut to throw on hot cams and larger carbs (or throttle bodies) because these are bolt-on go-fast goodies ...completely misunderstanding what these components do and how they
interact with the rest of the engine. So it must be clearly "faster" ...when in
fact, it is not! Speed is measurable and not subjective, unlike tone. Changing PI tubes clearly creates tonal
differences; but only one's ears and personal tonal preferences can decide on whether it is indeed "better." I hear you though: change for change's sake is not by definition an improvement. One must be honest about that.
FWIW, I have played out quite a bit with my DC5 with a NOS Mullard CV4024 (12AT7) in there, hmmm for a couple of years now, and no maladies. Not that this "proves" anything, of course, but only to say so far so good, with nary a hint of any operation differences ...only "better" tone!
Who knows how other amps will behave. But again I submit that until someone says how (if at all) the spec difference creates actual risk, especially in light of others (like the author of the paper) endorsing such a change, it is likely we may be making something out of nothing.
Edward