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Output Transformers
  • Ok. The other upgrade I want to make to my 65 PRRI is to the output transformer. It seems pretty simple to get one from Mercury Magnets but what about Hammond? The only problem is I knowing which is correct for my amp. It's pretty straight forward on the Mercury website but not so much on the Hammond site.
  • From my notes, "upgrading" the OT made little, if any difference. What are you trying to achieve? I tried several mods on a PRRI and found some helped, some weren't worth bothering with. A new speaker is PARAMOUNT. don't do anything until after you get the new speaker in there, it changes things quite a bit.

    PS- you can also get a new OT from Allen amps, that's where I got mine. On my next PR, I won't bother changing the OT because it really didn't "help" at all.
  • That's interesting and good to hear. Really again I'm just looking for a little more clean volume from my amp but don't want to change it's character (too much). John Fromel likens upgrading the OT to "taking a heavy blanket off your amp". so it piqued my interest. Will definitely start with that speaker swap...
  • This is just my opinion, but Fromel is full of it. The new OT has about 5% of what you're looking for (more volume and headroom), the Weber has the other 95%. Besides, when has anyone EVER complained the Princeton Reverb sounded like it "had a blanket on it"???? Keep in mind: Fromel was making money selling mods....

    Just think about it: what's the biggest difference in the vintage PR and the PRRI, since they are the same circuit? Not including the difference between handwired and PCB (which a debate rages over whether tone is affected; I fall on the side of it is NOT... handwired has benefits, but "more tone" is not one of them)?

    The speaker.

    That Jensen C10R is just not a good speaker for anything other than low volumes (it actually sounds very sweet at low volumes... perfect for apartment/bedroom playing, clean). It just can't handle the volume or bass the circuit puts out. A Jensen C10N (which was in the vintage versions that had Jensens) CAN. Jensen no longer makes a C10N... so the Weber is the next best thing.
  • I agree totally about the C10R. I wonder why they stopped making the C10N since it seems to be the speaker everyone wants? I go into any changes to my gear cautiously and definitely one thing at a time and it will be the speaker first. The only other upgrade I've done I was forced into when one of the 6v6's went and I replaced them with the Gold Lion's. I was surprised by the difference which just had me thinking about ways to get the best from it while still keeping it a Princeton. Not into mods but upgrades.

    With that in mind, I'd be eager to hear any other thoughts you have on "stock" upgrades. Thanks
  • Well, the only other "upgrade" I did, besides the speaker and OT, was adding a power supply filter cap, it "stiffens" the power supply up a bit, which basically means it helps to firm up the low end. It made a bigger difference than the OT did, but the speaker was still the key. I did the speaker LAST, on purpose, to learn how much difference these other mods/upgrades make. The speaker really is the weak link. Replace it, and I bet you'll be MUCH happier.

    When I get my next PR (I sold mine, stupidly), I will replace the speaker. That's it. I would only consider the filter cap addition IF the speaker wasn't enough (and I think it will be.) But based on my experiments, I wouldn't mess with the OT at all.

    As for headroom, I didn't think to ask before but... have you made sure the amp is biased properly? They usually come biased cold from Fender. I bias mine hot- just like Jim does (info is on his website).
  • +1 on everything ruger said. I did the OT upgrade as well. To my ears, it made a small improvement in the tone and only when using dirt pedals. But a good speaker made a much bigger difference. I also did the filter cap mod. Again, that improvement helped more with dirt pedals. I think it was a bigger improvement than the OT but not as much as the speaker.

    If I had to do it all over again, I would do the filter cap (it's a very easy and cheap mod) and the speaker. That's it.
  • I actually didn't know about biasing until a few months ago so I think I will have it looked at. I will look into the filter cap as well. Thanks again guys

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