Which pre amp tubes do the most to voice a amp?

I understand the most voicing is from the first position. In my amp the 4th position in the pre amp tube for the fx loop so i beleive this has least effect. Essentially my question is this...i switched v1 to jj's low gain pre amp 8cc...(something) and the results were outstanding over the original crappy mesa tubes. Essientlly is there MUCH more improvement to be had from replacing v2-v5 with jj's? The reason is too save cash on tubes. Im fairly certain the power amp tubes should all be replaced. Thanks.

There can defanately be improvement from replaceing EVERY preamp tube. Even an FX loop and PI drivers, though not as much with these two spots. V1 will defanately effect your tone the most, but the others will make a big difference as well. Don't just limit yourself to JJ's. JJ's are great for an amp that has a naturally bright characteristic, since they tend to be a little darker than other tubes. Since preamp tubes are fairly cheap, I would get a couple different kinds and try them out in all the positions to see what works best. I would definitely suggest trying out a JJ ECC803 which is a long plate 12AX7, but has a fatter tone (to my ears). A JAN Phillips 5751 has a bit less gain than a 12AX7, but still lets you keep the sizzle. 9th Generation Shuagong 12AX7's are nice as well.

If the JJ you're talking about is the ECC832 (12DW7), then it definitely a nice tube, but it is very pickey about the amp it's played in. I've tried one in a Peavey XXX, 5150, and a Peavey Rockmaster preamp (yes, I like PV's). It worked great with the XXX, sounded like butt in the 5150, and was decent in the RM.

I would drop Doug a line at Dougs Tubes. He's alway's been real helpful to me, and has a nice selection of tubes.