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arrrghhh… now I’m on a tube hunt! For three different amps. Need to get it all together, so I’m not going piecemeal.
Originally Posted by darkwaters
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.
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06-07-2026 11:30 AM
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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.
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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.) Originally Posted by MiniMerckx.22
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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. Originally Posted by MiniMerckx.22
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.
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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.
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That's a different subject, changing to a lower gain tube for a sonic reason. I was speaking more about someone who has a tube go bad or they buy a used amp and just replace everything just to start over with all tubes of the same date.
Originally Posted by coyote-1
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I found a pair, RCA. Yeah they’re nice. Noise level is reduced, tone is great.
Originally Posted by darkwaters
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RCA? Well done. They’re my fave NOS 7025 tube. Originally Posted by coyote-1
12ay7s are my favourite way to calm down a Champ-style amp (the Tasmanian Devil of amps), but the 7025 is my go to tube for a larger amp. It keeps the beef, while reducing the noise.
Enjoy!
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Glad you found a solution that improves your PRII tone. Originally Posted by coyote-1
As great as these hand-wired, point-to-point amps are, (thank you Paul Rivera), I've seen quite a few users who continued to tweak them to fit their personal, sonic desires. Mine has been tweaked to suit my tonal tastes. Now it sounds great for jazz, pop and rock, but any overdrive is from an external pedal. No matter what tubes I've rolled in this rig, the internal overdrive is painfully useless. (I'd love to send my PRII to Andy Fuchs for his tweaking, but that ain't going to happen on my budget).
This thread has been very informative!
Here's a site dedicated to the PRII (and other Rivera-era Fender amps): Unofficial Fender Princeton Reverb II page
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Been looking at that page for years. The tweak I want to do is move the reverb tank, but the most difficult screw to get out would require I remove the speaker. It’s too stuck to remove it with the speaker in there. So it won’t get done for awhile; I want to PLAY the amp instead of disassembling it. Originally Posted by Gitfiddler
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Hi... On the PRII, a 12AY7 is worth a try in V1 - even lower gain than 7025.
In V2, a 12AU7 gives you a really sensible range of reverb adjustment. If you're worried that it won't last because of the current demand, use a 12BH7 which is like a lower-gain 12AT7 with the 12AT7's current -handling.
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Thinking on it a bit… but not sure I’ll need it. I’m not going to use the “lead channel” function, and while more range for the reverb knob would be nice it’s also true that I can get what I want with it as-is. I just have to be precise! Originally Posted by Stratopastor
The only NOS 12BH7 tubes I’m seeing around at a price I’d be willing to pay are 12BH7A, and things are working great right now. Everything else is used. So I’d be leery of the spend, only to end up with a possibly noisy or microphonic tube, for that particular function.
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Having installed the 7025s in V1 and V3, I dropped my presuppositions and played with dials a bit.
Here’s what I found: the Lead channel is VERY useful, in more ways than one. I’ve got a very good all around sound for my Eastman using it. Only the barest hint of breakup. This configuration generates even less of a noise floor than before. And it gives just the right amount of reverb, with all kinds of range on that dial! Here are the settings, with the Lead and MidBoost engaged:
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Wow, all it takes is some dial twisting! I find very useful tones in the OD channel.
Next I'll have to sample your settings - there's so much range in these little buggers.
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Also, don't forget about the speaker. These 22 watt (solid state rectifier) rigs respond differently, depending on speaker efficiency, type, composition (AlNiCo, Ferris, etc.).
Mine has an EV12L that sounds best at higher volumes, and just 'OK' at bedroom levels. YMMV.
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Mine has that same EV12L (Fender branded). It sounds great at the volumes at which I like to play, so I can live with it being less than stellar at bedroom level. Originally Posted by Gitfiddler
EDIT: after playing it some more, I’m happier without the MidBooost engaged - but with the Mids knob at 10.Last edited by coyote-1; 06-19-2026 at 01:09 PM.
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