Advice On Tube Swap In Marshall AVT20?

[colchar]

I recently picked up a Marshall AVT20 for use as a secondary amp. It is my first experience with a hybrid amp and I have to say that I am more impressed with the amp than I expected to be and that it looks like it will suit my needs perfectly.

That being said, the overdrive channel has a bit too much gain for me. I was reading over on the other Marshall forum that someone had swapped out the stock tube for one with a lower gain factor - they had gone from a 12AX7 to a 12AT7. Apparently this gave a bit more headroom on the clean channel (headroom isn't an issue for me but I don't mind if that is increased a bit) and smoothed out the gain on the overdrive channel. Some others swapped theirs for a 5751.

I was wondering a couple of things before I go ahead and do that. First, has anyone here put a tube with a lower gain factor into their AVT or other Valvestate amp? If so, which one and how did you like the results? Second, since I know squat about tubes I was wondering if anyone could recommend whether I should go with a 5751 or a 12At7? Or might that simply be a personal preference thing? And finally, should I buy a JJ, a Groove Tube, EH, or whatever other brand?
Thanks in advance.

[Mike_LA]

Haven't tried using a lower gain tube in the avt20 that I have laying around but I did put one in my Vox AC4 and it gave it waaaaaay more headroom.

Those valves are pretty cheap, pick up anyone (except a JJ, nod to Surf) and throw it in and hear what happens.

The 12AT7 is a 40% reduction in power over a 12AX7

[colchar]

Thanks.

The guys over on the other forum seemed to be using Jan Phillips tubes but they are not available at my local store so, instead of ordering one from somewhere, I will grab a Groove Tubes or something to give it a try.

[Mike_LA]

yah, give it a try.
For what it's worth, tube types are pretty subtle in there effect on tone.
I changed all 7 preamp tubes in my 6101 for a recommended set and I didn't hear much of a remarkable difference for what I play and for my ears.
It was a pretty expensive test for a slight change.
Speakers are where the money is for change in tones.

[colchar]

Turns out my store had bugger all in stock. I only saw my buddy the sales guy for a brief minute before I popped in to see my other friend who is their guitar tech. I needed my Muddy Waters Tele tweaked a little and, once we were done, the friend who is the sales guy was on break. I'll see him Friday and will get him to order me a replacement tube then.