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How much does the PI tube contribute to the tone of the amp? Is V1 the most critical?

I just picked up two NOS Mullard 12AX7's and two GE NOS 12AX7’s (along with 4 NOS matched EL84's and a 5AR4).

I now have a second set of power tubes to put away for the future but should I change all three 12AX7's including the PI or could I put a Mullard in V1, a RCA in V2 and leave the PI (if it is not as critical) and then save a set of pres.

Sorta like hording a complete change out for some special day.

Some say the pre amp tubes last for years and only the power tubes need to be changed.

Oh, the current tubes are all Grooves' but the are starting to snap crackle and pop during warm up.

I'm sure there are many theories on this one. For my money, V1 is where I'd place to put the Mullard.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

I've been wondering about the effect the tube in V1 has, so I did a little experiment. I took a Mullard CV4004 and put it in V1 in place of a Sovtek 12AX7. The Mullard came out of a Fender Pro Reverb that sounded great since I put it in. I thought I'd have this vastly improved, warm mellow tone, but amazingly, I prefer the Sovtek. The tone was warmer, but much quieter. It didn't have the snarly bite of the Sovtek. Some may not like this, but I think it gives the amp character and really makes it sing at higher gain settings. To each his own, but for now I'll stick with the cheap russian tubes.

Moid

This really depends on how the circuit is constructed. Conventional wisdom sez V1 has the most effect on tone. This is really more myth than reality. The truth is different triodes in an amp are designed to shape the tone in different ways (at least in sophisticated amps). So the characteristics of a tube should be balance with the characteristics of the gain stages at that position. What it boils down to is you should choose with your ears rather than any arbitrary formula.

What is true is V1 should be a very quiet tube since any noise it creates will be amplified thousands of times before it reaches the speaker.

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--s2
www.s2amps.com
www.category5amps.com

I recently finished my Spitfire build, and used a Groove Tubes 12AX7M-MPI (Matched Phase Inverter) that I bought from Revolution Guitar on ebay. Supposedly these are new builds of the Mullard style tube, with matched triode outputs for sending an equal signal to each power tube. I've read on this forum that the Spitfire and Lightning are really PP amps, so why not? A little pricey at $24.99, I guess - but , how much would a NOS matched Mullard cost?

I've been running an old ecc83 that was not matched, though reasonably close on my Eico 666, and so far I can't say it sounds any different. I'm gigging it Friday night, so I'll have a chance to listen all night in a band situation. Time will tell, or not...

I also put a GT 12AX7M in V1 (yes, a Mullard style), and I have to say the amp does sound sweeter than with the MESA 12AX7 that was in there.

So many tubes, and not enough time to try them all... Well, maybe.