Amplifier Power tubes - important to sound?

 I have the rogue Apollo monoblocks which use 12 Kt88

I have 3 sets of tubes. Golden lion  Electro Harmonix Kt90 and  Kt120.

The 120 are colored in my application.

The kt90 and sharper and firm the gold lion I give the nod to good luck

I have the rogue Apollo monoblocks which use 12 Kt88

I have 3 sets of tubes. Golden lion Electro Harmonix Kt90 and Kt120.

The 120 are colored in my application.

The kt90 and sharper and firm the gold lion I give the nod to good luck

@hiend2 I’ve also used all 3 of those tubes in Apollos. Totally agree with your assessment there. EH KT90 were bright / sharp. Gold Lion KT88 was the best, and my fiend with Zeus (now he has my Apollo Darks) agreed too. The effect of power tube rolling is typically VERY clear! Tung-Sol 7581A sucked by the way. Now I feel stupid for trying it, and I still have 12 of the damn things. 

KT120 was my favorite with all of VAC’s amps, though. You could definitely say it’s a bit colored, but the way it turns out in the VAC amps really works for me lol. I can see why most prefer the GL KT88 there too. But I simply can’t understand how anyone liked KT150 in these amps.

Recently bought a matched quad of 1st generation Genalex KT88 to replace some Winged C 6550 that I thought were terrific; paid what I felt was stupid money for the Genalex (of England) but had to give them a shot given their description. The Genalex are from 1955 and came in crumbling boxes. I mean these things are OLD, lol but I have to say, two weeks into them now and I've realized the hype is real. Just a thicker, more robust sound in every way. Hard to use superlatives that havent been beaten to death but they are muscular and broody tubes that really changed the complexion of my system and I'm totally smitten by the way they play. Like realizing a new set of speakers or cartridge for the 1st time; they are impactful. I'll agree the prices on some on these old tubes is getting out of hand however in my instance, was worth the spend but, I do still believe that swapping out small signal tubes yeilds the highest level of change, in my linestge & DAC anyway. If you've got the means, and many on this site do, find a reputable tube guy, listen to what he has to offer and take the plunge. These old tubes wont be around forever and non of us are getting any younger. Just my experience 

Do power tubes affect the full freq spectrum or is it more focused on below 250 hz?

Do power tubes affect the full freq spectrum or is it more focused on below 250 hz?

Of course it is a full spectrum impact. Who is claiming otherwise, and how? If I cared most about below 250Hz, I’d run solid state.