Re-tubing my Princeton Reverb II

[coyote-1]

If you can find one, try a NOS 7025 in V1. I think you’ll be pleasantly surprised.

arrrghhh… now I’m on a tube hunt! For three different amps. Need to get it all together, so I’m not going piecemeal.

For the PRII, yes as quiet a V1 tube as I can find that still has good output. Along with at least one 12AT7 for V2.

For the Marshall DSL40c, I’d love to find a hybrid that is 12AX7 in the first half and 12AT7 in the second half. That would tame the HiGain channel. All I’m seeing is the 12DW7, which is half AX7 and half AU7. I’m not sure the circuit will like the AU7 part.

Likewise I’d like a similar hybrid for a Pro3T rotary speaker I have, again to tame the breakup just a bit.

[MiniMerckx.22]

There is absolutely no good reason to replace a functioning tube. The fact that other tubes of the same manufacturing era in the same amp have died is in no way related to how long that working tube will continue to work withing spec. Some tubes last decades. Have a spare within reach, sure but don't waste a piece of equipment that is doing what it's supposed to do.

[starjasmine]

There is absolutely no good reason to replace a functioning tube.

Depends on your definition of "functioning." Over the course of a year of a few hours use daily, preamp tubes lose tone and power tubes lose output. This happens so gradually that you may not notice a difference. The amp still works, but the sonics degrade. Swapping in new tubes can be ear-opening. If you don't hear a difference, keep the new tubes as spares (or, what I do: use the new tubes and keep the old ones as spares.)

[coyote-1]

There is absolutely no good reason to replace a functioning tube. The fact that other tubes of the same manufacturing era in the same amp have died is in no way related to how long that working tube will continue to work withing spec. Some tubes last decades. Have a spare within reach, sure but don't waste a piece of equipment that is doing what it's supposed to do.

Yeah there is good reason. As it turns out, back when these were produced Fender specified 7025 tubes for V1 V3 V4. Those were the low-noise version of the 12AX7. The amp currently has 12AX7s in those positions. So if I can locate good 7025s or whatever is the least noisy and least microphonic iteration of this tube, it will likely help.

In the Marshall, the “ultra gain” channel is too shrill. I’ve modded the amp in a way that helps, but I’d love to get that channel tamed a bit more. Likewise the Pro3T is a bit noisy when pushed, and could use a bit of taming.

[Jimmy Mack]

How many times have I read: you can substitute other "lower" gain tubes for the 12ax7?
Many times. And it's true, it works. 5751's, 12AT7's, etc.

In my Fender PRII, I have had those tubes reside in VI. Lower gain, smoother response, great tone, smoother gain tones......

They work, but you have to try them to like them. All good, but the last tube in that slot is a JJ 12ax7, I forget which one, but it's the one that works there. Although it did not sound so good in an old Tweed style amp.