What the cool new 12ax7 for amps?

I got some more....and wanted to drop another little bit of experience because this is a perfect example.

I put the 803 in all three preamp slots....terrible. Whatever "color" the preamp tubes have becomes exponential. In fact, if you want to hear what a tube sounds like? Do that. But, then I never end up with the same brand of tube in all 3 (or 4) or my preamps. The 803 is lower gain than a typical 83 and heavy on the low mid/high bass. So three of them and this amp went from a high gain monster rock amp to....a gainy but kinda farty "classic rock" amp. I imagine putting the KT77s back in with all the 803s would put it into "master volume'd Fender" territory quickly.

So, wonderful color to have at your disposal--sounds great in v1 which cascades the side (in this amp) for the majority of the top boosted preamp dirt....but, beyond that, it's "too much of that". So, I'll put the EHs back in the second and third(PI) slots.

Whenever I get a new amp, I go through this rolling different tubes into it to find the best combo. I point that out because this really isn't as big a of time suck as it is right now....and some circuits are FAR more sensitive than others. Boogies will like their tubes because what you need mostly there is the exact gain in each side they test for--they are super cheap Chinese tubes, but they are tested to not change the way the amp's complex gain structures and options interact.....it's the "simple" amps where this is all more a thing.

PS: Despite what i said about the construction of the frame grid tubes regarding less microphonics, the ECC803s is a long plate tube. So better bass and lo-mid behaviour comes with still being susceptible at least for excessive microphonics...

Yeah you do, for classic amp circuits....until it's too much. So, for (modern levels of) high gain amps, you have to walk a fine, fine line....best to err on the non microphonic side.

One of the things I've noticed in this is that the "tested as new for LOW NOISE" Mullard that started this whole bit, is that it's got a microphonic resonance REALLY high up there....like, when I accidentally tap the metal chassis with the multimeter tip it "rings" with that metal on metal "ding"....so, it doesn't exhibit anything in terms of howling or typical "too microphonic" but it obviously has a particular bent towards those ultra high frequencies...which likely plays into it's appeal.