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So I bought a 65 Princeton Reverb Reissue and I like it. Sounds fine in my room, I don't need to break it up as I like the Fender pristine clean tone that goes with my archtops. Then I happen to try an actual Princeton Reverb vintage and **holy cannoly**: that sounds awesome and much better than mine.
So I started googling and learned that quality of the RI is substantially inferior than their vintage counterparts. In order to improve it, I swapped the speaker for a Celestion Gold 10 and noticed a significant improvement.
What other mods are recommended for improving a 65 Princeton Reverb RI in addition to swapping the speaker? I found this and also a bunch of awsome PsionicAudio YT vids, but wanted to ask the community what's your opinion and experience.
Ll.
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06-23-2025 11:13 AM
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Start with the Stokes mod and the Paul C mod. The Stokes mod changes the power supply of the phase inverter to the unused anode in the power filtering circuit. The Paul C mod changes the phase inverter tube from cathode bias to a fixed bias. Fromel Electronics has kits.
The transformers and power supply caps are also begging for an upgrade. Sunnyside Amps put an Allen TO-20 output transfomer in Tim Lerch's PRRI and he's been quoted as saying that he loves the improvement in tone. The FBFPPS Mercury Magnetics power transformer is said to be an improvement, as is increasing the power supply caps. I don't kow the recommended values, but there are many sources on the web.
For me, these mods are far more money and effort than they're worth. To put even another $500 into a PRRI seems excessive. A better speaker makes a big difference, as you discovered. Beyond that, I don't think the mods are worth their cost, since even a hghly modified one doesn't sound as good as the original iMO.
FWIW, I used a Custom Shop BF Princeton for about 7 years and thought it was definitely better sounding than the production PRRI. It was close to my original, but still not the same. You do get what you pay for.
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Make sure you reverse the polarity of the neutron flow through the flux capacitor .
Joking aside, my ignorance of the dark arts of tube amp mods could probably allow someone to sell me just about anything, had I any money, which I don’t. Also confirmation bias…
I got an Eminence L’il Buddy speaker and put it in, and it’s a solid gigging amp. The stock speaker is dog meat. You want something with a high sensitivity. The Eminence is sensitive but it rolls the treble off… which may not be to your taste.
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To get closer to that vintage sound, you'll need to rebuild the whole thing:
Hoffman Princeton Reverb Board Build
Start with a new board:
To this:
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I have been using my '79 silver-face Princeton almost 30 years!
A tech has maintained and modded it very slightly but the biggest improvement was cutting the 10" baffle and installing a 12" Celestion Blue speaker. (I think they call it Alnico or Blue-Bulldog) It's the same as your gold with less power rating.
The reissues don't sound/feel the same. The reissue Princeton (hand wired I think they call it) is very close to my '79 but is probably 2-3 times more expensive than your reissue.
You can hear my original Princeton on most of the videos that I have posted on this forum, with a few exceptions where I am using a Headstrong, (which is basically a more powerful Princeton clone)
Hope that helps!
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TBH I am trying to understand if it makes sense to "rebuild the whole thing" (as in, substitute the PBC with hand wiring circuitry), or just do something else as Stokes/PaulC mod.
I mean the alternative would be to sell it, and get the real thing, or perhaps a boutique amp? But maybe if I throw $500 at it will get "good"?
Just I don't really know how good per how much $$ so your opinions are appreciated here
Ll.
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Only you can decide whether or not you want to put a lot of money into it.
Rebuilding it doesn't make much sense to me. A speaker change and a couple of mods would be the most I'd do.
If you would rather get a "better" amp, then you could get a hand-wired Princeton or even better look at the Headstrong LiL King or the Louis Electric Columbia (a princeton with a 12" speaker and a bigger transformer). I have the Louis Electric and I'm very happy with it.
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It’s the Custom PR, and it’s now $3150! There was one in the backline at the club in which I played twice a week for many years. The club owner bought it (along with a SF Vibrolux production reissue) 7 or 8 years ago without asking me. My ‘76 PR sounds bigger, smoother, richer, and cleaner. When it starts to break up, it’s sweeter and not at all buzzy. The Custom PR is nowhere near worth its cost - there are many better boutique amps for less money, IMO.
Originally Posted by Question
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FWIW, in my neck of the woods (New York), it would cost a lot more than $500 to convert a PCB-board PRRI into a vintage clone. Given that you can a find late 70s's PR's for $1500-ish (which is as good as a BF or any custom clone of one), I don't think it makes sense to to that. Changing the speaker (which you've done), and maybe swapping in some better tubes, yes. But unless you can do the work yourself and are looking for a project, better to sell it and put the proceeds toward the amp you want.
Last edited by John A.; 06-23-2025 at 03:42 PM.
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I personally wouldn't go too far with it. Princeton reverb doesn't have much headroom at its best. To get it to its best, you would essentially be changing everything except the cabinet and chassis. It is what it is. Lots of options out there for a Princeton sound. Originally Posted by Llewlyn
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From a reliability standpoint, a completely rebuilt reissue amp might be risky.
A free and easy test would be to connect the speaker out of your reissue to the 12" speaker in another amp with a similar cabinet size. You might be happy with that and you could hear it before you modify your reissue amp.
I suspect a 12" speaker change would be a bigger improvement than changing components.
As mentioned by Freddels there are other (more expensive) options. I have a Headstrong lil' King, which is also a more powerful Princeton clone.
I think that is the amp that you hear in my "Giant Steps 2025" video. Very similar tone to the Fender with a bit more midrange.
Good luck!
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My boutique version is a Fat Jimmy Gigmaster, slightly more power and a bit different circuit, great amp. Originally Posted by Freddels
There are many companies out there with different flavors of Princeton and Deluxe Reverbs.
BTW, I have a real BF Deluxe Reverb and have for 40 years, and I mostly use the Fat Jimmy. It is a warmer sound and better for jazz.Last edited by bluejaybill; 06-23-2025 at 03:26 PM. Reason: Add information
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OK some consensus is emerging. So some tweaks yes, but not expensive rebuild.
So this is what I am thinking:
- Add an external bias pot + test points
- Stokes + Paul C phase-inverter mods
- Tweak mid-point / bright-cap for more jazz sounds.
Overall, it should be a 1hr work and cost a $100 - $200 or so
Ll.
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It's really just the speaker, the P10R isn't good at much except very low volumes (and it's very sweet for that). I modded the crap out of a PRRI, different speakers, added a filter cap, NOS tubes, re-biased (they are usually biased cold from the factory), even put in a midrange control.
Honestly, don't waste your time. Just find a speaker you love in it and GO. That's 90% of the battle with those amps. If I were in the market for another Princeton, I'd actually get the new-ish 68 Custom VIBRO Champ Reverb... that thing needs nothing. Sounds fantastic from the get go. I might actually get one...
I had a PRRI with a 10" that I modded the crap out of, and also a gorgeous knotty Pine Princeton with a 12" Celestion Cream... that thing was awesome. I just like more mids than the blackface circuit provides, and the '68 Custom amps have it.
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I had a Princeton Reverb RI and I changed the speaker (Weber 10F-150T 50 Watt), the output transformer (Allen TO-20) and tried solid state rectification (diodes). While those changes made a big improvement, it still did not sound as good as the real thing. If you want the tone of the real thing, get the real thing (that is what I eventually did).
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You might want to also consider a speaker upgrade to your list. My '69 Princeton Reverb really benefited from an Emi 1058 Legend. Originally Posted by Llewlyn
It's just one of a few nice speaker upgrades to consider.
10 inch Eminence Lead / Rhythm Guitar Replacement Speaker
– Eminence Speaker, LLC
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I already put in a Celestion Gold 10. Very nice upgrade, esp on bottom end.
Ll.
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Oh yeah... I knew I forgot something. I also did the Allen OT. Originally Posted by Stringswinger
So, I did
re-bias
allen OT
NOS tubes
extra filter cap
mid control
different speakers
... and the speaker is 90% of improving that amp. There's nothing "wrong" with the circuit; but the new P10R just isn't good for much but low volume home playing.
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While I enjoy mods and complete rebuilds, a speaker swap is easy and will get you closer to where you want. Another easy fix is replacing V1 with lower output tube such as a JAN 5971. Originally Posted by ruger9
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LOL at this thread. "Spend as much as a used SF Twin and your PRRI will sound better"
At some point in the $$ soak it's just time to find a better sounding amp, of which, there are many.
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I’ve owned mine for over 10 years now and I’ve never regretted buying it. I’m sure for triple the price I could’ve gotten something even better, but, I’m a hobbyist these days with a not unlimited budget.
I’ll echo others here and say that the original speaker is just so so. A speaker swap is a (relatively) cheap way to greatly improve the sound IMHO. I had a vintage 60s alnico 10” that I swapped in and it made a big difference.
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There’s no reason why a well-designed,well-implemented PCB amp can’t sound just as good as a hand-wired one. You will have more consistency with a PCB, good or bad, because wire dress is so important in a tube amp and a PCB rationalizes much of that.
A circuit built on a tab or turret board will probably be easier to troubleshoot and repair. Point-to-point wiring on something like an AB763 would be a nightmare, though.
Building an amp is never cheaper than buying the same amp. You don’t have the buying power Fender or Marshall has, and you are going to pay retail for the components. Then you have to assemble them, and it’s not just a more complicated dirt box. There’s a lot to it, and most people need to build a few before they are really usable amps.
As has been mentioned, a speaker swap is by far the most effective change.
The next most effective change is a tube swap in the input position. A 5751 has been mentioned (not a 5971, that was certainly a typo) or a 12ay7 (or mil-spec equivalent).
If you replace all the (mf or cf) resistors with vintage-correct carbon comp, the main difference you hear will be increased hiss.
To increase headroom, you can increase plate voltage on the preamp tubes, you can cold-bias the output tubes, you can switch the cathodyne phase inverter to a SF style LTPI, but all that turns your amp into something that isn’t a Princeton. Just buy a Twin.
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Thanks guys -- very useful perspectives.
It seems that a speaker change may be the sweet spot. As per tubes, I may need to replace them anyways at some point and I may be looking for an upgrade.
Ll.
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Preamp tubes such as V1 and V2 in a Princeton can last for decades. It is usually the power tubes (V6 and V7) that often do not last more than a year or so with heavily played amps. Replacing V1 will have a subtle effect compared to a new speaker (remember to allow break in time for a new speaker) but keep your eyes open for NOS tubes. You may come across a bargain. Originally Posted by Llewlyn
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Agreed, i just don't get this madness with modding/ upgrading stuff out of the box. If something breaks, or has a defect, sure go for it. Otherwise big Originally Posted by DawgBone
. Just buy the right piece of gear in the first place.
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