Princeton Reverb "tune up" vs. Blues Jr

[stratopastor]

Hi guys,
New to the forum. I made my first venture into tube amps about a year ago with the purchase of a Princeton Reverb (I think it's around a 73). This made me drink the Tube Amp Kool-aid. I don't play it very loud as it is usually mic'd.
I purchased today (used) a mexican Blues Jr. for my son for Christmas. I know these are different amps and won't sound the same, but I'm shocked by how weak and thin the Princeton is compared to the Jr. I also know it's a ten" speaker vs. 12" and 12w vs. 15w, but still the clarity and power difference is great.
I went from being very pleased with my Princeton to wondering if it needs a resurrection. One thing I notice is the speaker in the Princeton seems to fart out very early while the Jr. is clean and clear to the top. I doubt anything has ever been done to this Princeton except maybe a tube or two along the way.
So I came by here to see if anyone can suggest some things to check on the Princeton, offer opinions, or point me in the direction of things to check to see if it is in fact up to par.
I see Princeton Reverbs going for 800-1200$ and bought this Blues Jr. for $300, and if I were blindfolded, there is no way I would choose this PR over this Jr.
Suggestions? Thoughts?

Thanks in advance,
Brent

[Phil_S]

Hi guys,
New to the forum.

Welcome, nice to have you here!

....So I came by here to see if anyone can suggest some things to check on the Princeton, offer opinions, or point me in the direction of things to check to see if it is in fact up to par....

Chances are your Princeton needs service! It could be a variety of things. An experienced technician will know what to do. Obvious things are that filter caps need to be changed periodically and an amp this old -- even if already done once may need it again. Tubes don't last forever either. Neither of these routine maintenance items is going to clean out your wallet.

The perceived difference between 12W and 15W is almost nothing. So, if you are really hearing a difference, then something needs attention.

Where are you located? (Put it in your profile!) Maybe someone here will have a recommendation.

[Randall]

If nothing has been done to the PR, then it likely needs the electrolytic capacitors replaced. And if it is the original cheap Fender 10" speaker, replacing it with something better will make a big difference. All lot of people put a 12" in a princeton if it's going to be gigged. Lots of subjective choices here, but I would direct you to Weber VST as a good place to start. http://www.tedweber.com/

[vibratoking]

Yup, probably caps and power tubes are needed. Connect the PR to the Jr's speaker and see what happens. Some Fender speakers are known to fall apart in the lows. I replaced one with a pretty low cost Eminence and the difference was night and day.

[Gaz]

One easy thing to try would be hooking up the Princeton to the Jr's speaker to see how much if a difference alone that makes.

[Milkmansound]

the proper reaction to comparing those two amps is usually putting the blues jr either in front of a train or under a space shuttle as it launches.

so yeah, tune it up! search this forum for the magic Princeton recipe - its a good place to start after new tubes

[Leo_Gnardo]

There's a big chunk more gain in the Blues Jr, and although gain is not power, it can give the illusion that it is. Our ears interpret distortion as power - that's psychoacoustics for ya. (I could write a sermon on that point.)

By now the Princeton probably needs a good going-over. Scratch probably. DEFINITELY.

They are two widely differing amps. Both good. Viva la différence.

And don't wait for any space shuttle launches. There ain't gonna be any more. Hey milkman watchoo talkin' about? Don't worry, I know what ya mean.

[Milkmansound]

True. I guess it's a long drive to Russia

[stratopastor]

Wow! Thanks for all the responses, and the welcome.
I took the Blues Jr. to a rehearsal tonight and was very pleased with it's performance overall, except I discovered that that as it gets louder when dirty, there begins to be a strange noise, not the speaker, but when you hit power chords and let it ring ,there is a staticky noise sort of like a bad connection in the background.
But aside from that, the comments about the train and the space shuttle definitely make me think that my PR is not doing what it oughta.
Swapping speaker connections is a great idea, and I will try that tomorrow to see what that reveals.
Thanks for the input!

[Firestorm]

The other thing with Princetons is they're fixed bias, but non-adjustable. The bias set resistors drift so they can get too hot (which makes tremolo barely work) or too cold (which thins them out something fierce).

[martin manning]

I recall there is a known cabinet vibration noise issue with the BJ.
+1 on new e-caps, tubes, and bias check for the PR.

[Leo_Gnardo]

The other thing with Princetons is they're fixed bias, but non-adjustable. The bias set resistors drift so they can get too hot (which makes tremolo barely work) or too cold (which thins them out something fierce).

All true. But you can have a bias trim pot added (costs a couple bucks at most) while the rest of the Princeton is being refurbished, then have the bias set just right.

Another way to squeeze a couple more clean watts out of a Princeton is use a 12AT7 as an output drive rather than 12AX7. But this has the effect of reducing the vibrato depth. No worries, vib depth can be restored by bridging the 1 Meg resistor that delivers the vibrato signal to the depth pot with another resistor 220K to 470K.

The rattling in your Blues Jr at full crank could be cabinet rattle as Martin says, and can also be the sound of deep clipping, also a speaker in distress - kinda ratty. That's rock n roll for ya! Get loud enough and even your eardrums will start to rattle, though that usually takes a couple hundred watts & big speaker cabs.

[Milkmansound]

with blues JR I find that there can be a lot of "static" sound from fractured solder on the output tube pins. With high SPL, that may be a factor besides any physical rubbing.

also true for the pins on the input jack on the circuit board - they often fracture