Add Gain to a '69 Princeton NR

Are there any simple mods to add some gain to this amp and make it louder or should I just sell it and move on to something else?? I got it for nearly free form a friend but in its present form, it's barely louder than a Champ. I hoped it would sound similar to my old Princeton Reverb, but no dice so far.

Don't hack mod the damn thing. First off make sure it is healthy (caps, tubes, etc.) Put in a more efficient speaker like a Weber 10F125. If it still needs "more", use a drive pedal. If that still does not cut it for you, get a different amp.

Don't do anything that will overstress the already maxed-out PT or it will fry. Read the other threads on Princeton power transformers.

Listen to the man!

A good clean boost pedal will do everything you're asking, and won't mess with the amp.

Tim

Put in a more efficient speaker

+1! What speaker is in it?

First off make sure it is healthy (caps, tubes, etc.)

+2! Don't throw the baby put with the bath water! Those are great amps and should have more SPL than a champ. Make sure it's bits are in good order before selling.

I had a really great, really toneful 1966 BF Princeton (non-reverb), and it really wasn't very loud, compared to a Princeton Reverb. On 10, it was about the same as 6-7 on a PR. And it stayed pretty clean, as well. Damn, though, was it TONEFUL!

Just saying...

Tim

A PNR on 5-7 is still much bigger than champ. Just saying.

The PNR has several dB less preamp gain than a PR. Hence my suggestion for a drive pedal to make up the discrepency. It has the same/identical power output section so it's max power out is the same.

Stock speaker in these amps, IMO, sux. Oxfart 10J4. A Weber 10F125 is *way* more efficient.

If you have an older one with the screw mount baffle, you can buy an aftermarket baffle (or make one yourself like I did) that holds a 12. Again, massive improvement over the stock speaker. I put a Weber 12F150 in mine.

Lastly, if you'll notice, there are actually 3 screw holes for mounting the OT. The stock OT uses the closest spaced pair. It just so happens that a DR OT fits perfectly in the wide spaced pair. No drilling. If you are going to go to the trouble of replacing an OT in a Princeton with anything aftermarket, why not go with the bigger DR type?

Done all the above on mine. It's as loud as my DR.

IF the amp does have the Oxford speaker, it is indeed a low-efficiency speaker. STarting in the mid-60's 1966? or so, Oxford started buidling a sider gap in their speaker which decreased the efficiency. EArlier OXfords do not suffer from this and can be good speakers.
It is probably time to get a tech analysis of the amp. Worst case scenario, your OT is not performing up to spec. THat amp should be a bit louder than a Champ. Hey, put the PRinceton through the Champ speaker for a few seconds and compare the output through the same speaker. THat should give a clue as to what is going on. Best comparison would be through a 4 ohm load that is separate from either amp....just to be safe with the Champ's speaker.

We are in exactly the same boat--I found a pristine '69 Princeton NR. I was really surprised that it wasn't as loud as my '71 VibroChamp, but I wanted a cleaner sounding amp. With a clean boost, it's great--I have a SexDrive and a Keeley Katana. The Katana is darker sounding, but really gives a nice bit of hair around the edges. I have had a hard time finding an OD pedal that didn't sound fizzy, but am using a Barber LTD and its a great combo.

As for mods, mine is in the shop now to add an adjustable bias, which should help with the relatively weak trem, and I'm also doing the Paul C and Stokes mods. They each involve only moving a wire--they aren't going to ruin the amp--and my understanding is that they will add both volume and some oomph to the amp. I'll let you know how they sound...

If it were mine, I'd sell it and buy an amp that did what I wanted. The Paul C and Stokes mods can take there tolls on the PT.

If it were a player amp and not a collector piece, I'd add a Mid/raw control, the raw takes the tone stack out of the circuit and increases gain.

A few comments:

First, thanks to the missing reverb circuit, the PT on a non-reverb Princeton is not as stressed as the same PT on a Princeton Reverb.

Second, I owned both blackface and silverface non-reverb Princetons, and though I had heard about the extra hole in the chassis for a Deluxe-size OT, I didn't find those holes on my amps. Perhaps those extra holes are only on Princeton Reverb chasses?

Last, to second, third, and fourth what others have said: in the end, you might consider letting this amp be what it is. It is a delightfully toneful little package, especially with the right speaker. The 10F125 is a good choice. If you were to keep things clean, a new Jensen C10R sounds wonderful in a straight Princeton. Eminence Copperhead, Ragin Cajun, and Legend 105 speakers would also be good choices with louder voices than the stock speaker.

Bob Arbogast

If you want it dirtier, install a 1K resistor in parallel with the 1.5K cathode resistor (tied to ground on the control-panel side). That will lower the total resistance on the first triode of the 12AX7, increasing gain. I just did this on my 5F1 after alligator-clipping different resistors in that position, settling on 1K. This lowers the resistance to ~ 700 ohms, and it'll dirty up the mids a bit and add a little volume.