12AT7 to replace 12AX7

[King Elvis]

I have a little amp that has two 12AX7 preamp tubes. I want to lower the gain a little bit so I thought of changing one of them with a 12AT7. Which position should I plug the 12AT7 to accomplish this?? Its a small 15w amp that has two 12AX7s for pre and 2 EL84s for power.

 

[Major Tom]

I don't know if there is a "rule of thumb" for this, but it won't hurt the amp in either position, try both. I did this recently on a similiar amp and I have it in position 2 so that it only affects the higher gain channel, (which was too saturated at any setting for me) the "clean" channel only uses the position 1 tube. It worked great.
I remember from one of your recent posts that you have a PV classic 20. With my limited understanding of tube amp circuits, I would try it in position 1 (farthest away from the power tubes) first - it looks like the classic 20 has 3 gain stages (#1 & 1/2 of tube #2) and uses the remaining 1/2 of tube 2 as a driver. The first half of tube 2 is right before the tone stack and the second half of tube # 2 is a "driver" tube for the power tubes, the AT7 might not be able to drive the EL-84's to full volume, Anyway, it won't hurt anything....

 

[King Elvis]

Alright MT...
I really appreciate the response. I was just playing thru the amp and... well the amp sat in the closet for the past couple of years as I have been using a POD to record with and stuff. I just never really appreciated the tone of this thing until now. I may not even mess with it at all. It has such a sweet tone and I can adjust it to sound clean if I need too. I have had this amp since about 1994 and I feel like a dumb a**, I have been searching for such a great tone and it was sitting in the closet!!!