Ok, I tried the swap, and first of all 12AT7 in V2 of Mark V:35 works. Here are my two considerations:
PROS: slightly improvement in tone, honestly barely perceptible, less hight that leave some more space to the low-mids
CONS: less gain, I mean, I know they are intended for such use, but seriously, you lose the character of the Mark V. You can't get that liquid sound for shred or something faster, moreover with the smoother high you lose the harmonics
CONCLUSION: I put back the 12AX7, dialed some different tone and re-evaluate the power and versatility of the V:35. My question was: ok, who am I to assume I'm better than Mesa Engineers and to change a tube for another? Anyway this last video gave me more inspiration as well:
https://youtu.be/JD6Tk7SpR0E
In the comment of the video someone from Mesa Boogie reply to a question similar to mine:
USER: nickardasis
Amazing player, and as always Mesa delivers the best product demos/videos. I've never used a Mesa amp before so I have a simple question, this or the TC-50? What are the tonal differences and what is essentially the "Mark Sound"? Which one is more versatile (I play from jazz to metal) and which one is more usable for home use? Both are very similarly priced in Europe so I need to know some of their differences. Thanks.
MESA/Boogie
Hi Nick - Thanks for the kind words and thanks for your interest. Mesa Mark series circuits are a very unique sound compared to, say... classic circuits like British or American circuits. It's tighter and more accurate, very vocal for lead sounds, and also very tight and heavy for high gain rhythm sounds. Cleans are also incredibly clean, detailed and sparkling, and also clip nicely. Like all Mesa's, Mark series amps are very versatile and cover lots of tones, and people love the powerful 5-band graphic EQ for additional sounds or.
The TC50 is more of a British circuit, and while it's also a tight, accurate overall circuit, the gain layering and the low mid punch are identifiably British. It's an easy question to ask (to compare two amps), but it's really best answered by sitting down with them both at your local dealer if possible. You have to hear it, but more importantly - feel it - to decide what works best.
The TC50 might be slightly more plug and play but lots of people become Mark series devoted once they spend enough time with a Mark and then really identify their sound with those circuits. Let us know what you find out when you have a chance to check them out!
I don't want a Mesa that simulates a British amp, and I don't need a plug and play amp, I'm not at that entry level. So I'll keep the Mark V:35.
I thank you all for sharing your opinions and experience here! 8)