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FDP Forum / Fender Amps: Vintage (before 1985) / Tube question for Princeton Reverb or any vintage tube amp

Contributing Member

Northwest Missouri

Butterscotch Blues
Oct 26th, 2018 09:14 AM   Edit   Profile  

I just got an email from stew-mac on how easy it is to change all of your tubes. Even a video.

But, I didn’t hear anything about rebiasing if you change power tubes.

Isn’t that a given?

Since I don’t know how to do that, and not wanting to fry the amp and myself...

Contributing Member

juneau ak.

If you must smoke, please smoke salmon!
Oct 26th, 2018 02:12 PM   Edit   Profile  

I've changed power tubes in my old Fender amps more than a few times and never bias them, I do try to find a matched set however, and getting the proper voltage for a particular tube is important for the over all life of a tube. Come to think of it, I had a tech check one amp out because it just didn't sound right (it was running cold). In my opinion in most of the smaller amps the preamp tubes are going to make the most difference in the over all sound. V1 tube and sometimes the PI tube is where I put the best tubes I can get. Your results may vary!

PS I generally won't change a tube unless one goes microphonic or the clean headroom is lost, good tubes in a proper bias amp should last thousands of hours.

Contributing Member

So. Cal. USA

Oct 26th, 2018 02:31 PM   Edit   Profile  

The thing about not checking bias is you don't know if you got what you paid for in your new set of power tubes. It really should be checked and the amps tome optimized.

The Princeton is a bit different that most black face amps in that the Tremolo is bias shift so changing bias settings is not as easy as turning a bias pot on a Deluxe Reverb.

Contributing Member


Oct 27th, 2018 10:43 AM   Edit   Profile  

If your amp is healthy and set up right and your current tubes are good, there really isn’t a whole lot of audible difference in tube swaps. I’ve done a lot of it, over the years, and now I rarely swap out good tubes.

Contributing Member

Northwest Missouri

Butterscotch Blues
Oct 27th, 2018 10:44 AM   Edit   Profile  

Thanks guys. I’ll leave it alone.

Tony F

Long Island, NY

When you come to fork in road take it
Oct 27th, 2018 01:53 PM   Edit   Profile  

plus 1 on what Leftee said
I think I have a good ear and swapping one good tube to another is something I don't get. I think it's more the placebo effect with tubes as the differences which there may be are so subtle it's just not worth the bother.

FDP Forum / Fender Amps: Vintage (before 1985) / Tube question for Princeton Reverb or any vintage tube amp

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