Silverface Princeton reverb questions

speedtaco

Senior Member
Messages
913
Hi everyone – I was recently given a clean late 70s Princeton reverb amplifier. It's got the push pull volume knob on it. I was thinking about taking the amp to my tech and have him remove the push pull feature. I was also thinking about having him wire it to blackface specs.
I read recently that Princeton reverb amplifiers essentially had the same wiring throughout all the years they were made. This would make the amp blackface spec already. Is this correct?
Would it make a tonal difference if the push poll feature was removed?
Would it make a difference in the amplifier if it was modified to blackface specs if it's not already?
I'm asking these questions because I had a 72 twin reverb modified to blackface and it is a great sounding amp!
Any feedback is appreciated! Thanks
 

67super

Member
Messages
1,504
Very few changes were made to the PR and the push pull pot should have no effect when it is disengaged (pushed in). I would leave it alone to maintain the amps originality.
 
Messages
1,071
VERY minor changes in your amp from blackface. Mostly in the style/kind of components, not the value.
It would be easy enough to find the schematics or layouts online to compare.
When the pull boost is in, it's the same as earlier amps that didn't have it.
I kinda like the boost on my 79 Vibrolux.
A little smutty and anti-social.
 

zenas

Member
Messages
8,871
I'd just replace all the electrolytics, including the cap can, and add a bias pot. And anything else it might need.
Then play the snot out of it as is.
 

speedtaco

Senior Member
Messages
913
Thanks for all the feedback guys I really appreciate it! It is a great little amp. I put a 10 inch tone tubby Red alnico speaker in it, and replaced the original tubes. The new speaker really helps with the bass. I used to be kind of a blackface snob cosmetically, but I'm beginning to really like the looks of the silverface amps. It's no wonder fender started re-issuing them.
 

dcbc

Member
Messages
2,414
Sent my 76 (non push pull) to David Allen for a tune up and an adjustment to the PI circuit. When I asked him about blackfacing it, despite the fact that he already had modified the circuit (on the phase inverter), he said it was close enough already and not worth messing with. If you like the way the amp sounds, I agree with those who say don't bother with it and don't pull the boost knob.
 

tmac

Goldmember
Platinum Supporting Member
Messages
2,342
I agree with the above, get serviced & leave the pull boost. When you're feeling a little snotty or naughty just pull that knob and there ya go.
 

Mark 63

Silver Supporting Member
Messages
2,019
I had one for many years. If you don't pull the knob out, it has no effect. If you want a loud feedbacky sound, pull it out and give it a blast. The boost isn't as bad as it's made out to be. It's not very useful, but it isn't horrible.
 

Laurence

Gold Supporting Member
Messages
10,413
Just get it tuned up to spec (don't forget the speaker if it sounds weak), leave the circuit alone and play the crap out of it. This is when a decent set of NOS power tubes and preamp for V1 generally pays off. The boost has no effect when bypassed. The later years weigh more, and typically are louder/cleaner, but not everyone agrees.
 

mgreene888

Member
Messages
6
Hi everyone – I was recently given a clean late 70s Princeton reverb amplifier. It's got the push pull volume knob on it. I was thinking about taking the amp to my tech and have him remove the push pull feature. I was also thinking about having him wire it to blackface specs.
I read recently that Princeton reverb amplifiers essentially had the same wiring throughout all the years they were made. This would make the amp blackface spec already. Is this correct?
Would it make a tonal difference if the push poll feature was removed?
Would it make a difference in the amplifier if it was modified to blackface specs if it's not already?
I'm asking these questions because I had a 72 twin reverb modified to blackface and it is a great sounding amp!
Any feedback is appreciated! Thanks

Timely question! I am about to post a thread re my 1979 pull boost Princeton - in appreciation of the info I have gotten from this forum. The short version is this:

As background, I have had every blackface amp that I ever liked at one time or another in my life and I will say unequivocally that I love this "hated" pull boost amp. Listen to this amp before deciding to Blackface it or modify it. That said, mine was modded before I got it - all the brown turds were all replaced by CD-made orange drops. I was bummed when I opened it because I wanted to get a baseline with the turds (capacitors) and then strategically change a few. So what I did was make any needed repairs (a dry solder joint) and replace a bad tube and then listen. Boy am I glad I did! It had sounded terrible but after it was one of the best amps I have ever heard. It does not sound exactly like a traditional Fender amp but sounds really great none the less.

The big take away is this: IF you like the way it sounds, DO NOT remove the pull-boost components. Many threads say this offhandedly - "oh just dont pull the boost knob - no reason to remove the circuitry". Well being a casual know it all - I did remove it and all the mojo that I was so excited about was gone. The pull boost circuit has a ground from the plate of the reverb tube that seems to tame an ugly upper midrange emphasis in this circuit. With the boost stuff removed, it does start to sound more traditional fender - and I could see that if I wanted to blackface the circuit it would go there pretty easily.

Note that you can disconnect the pull-boost circuit from the pull switch - one side floats anyway and I sent the grounded side directly to ground. I used the switch for a simple mod that I will detail in a coming thread.

Mike
 
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Rhythm Rocker

Senior Member
Messages
2,642
Thanks for all the feedback guys I really appreciate it! It is a great little amp. I put a 10 inch tone tubby Red alnico speaker in it, and replaced the original tubes. The new speaker really helps with the bass. I used to be kind of a blackface snob cosmetically, but I'm beginning to really like the looks of the silverface amps. It's no wonder fender started re-issuing them.
If your SFPR had original 7025 pre-amp tubes, I would not replace them. I have them in my '79 SFPR and they sound great. Especially V1.

The newer silverface Fenders are not reissues, they are the Custom series. Nothing like an original '70s SFPR.
 

drbob1

Gold Supporting Member
Messages
30,224
My SF PR is a little earlier than yours (74) but it's one of the best sounding ones I've played. Every time I took it to a guitar show to demo a guitar I was trying to sell, I'd end up with multiple offers for the amp (and no one wanted most of the guitars)! I'd tune it up and try it out, if you like the sound at that point, and I suspect you will, leave it alone!
 

speedtaco

Senior Member
Messages
913
Again, thanks for all the great and thorough responses everyone! I actually removed the original tubes because I figured the amp would be more valuable if I kept the original tubes in working condition. I put JJ's in there, but I'm open to other suggestions on tubes!
Just out of curiosity, I'm wondering where you guys have your settings on your Princetons (As far as the treble and bass). I have my bass on zero and my treble around 5.5. Of all my Fender amps that's the only one that I keep the settings like that. All the others have the bass up pretty high
 

rusty

I own a guitar & I'm 3° from Kevin Bacon
Silver Supporting Member
Messages
2,710
shoot, my favorite vintage "house amps" ALL have old glass in them...the gig amp gets TAD stuff, but sittin in front of a vintage fender in your man cave deserves playing the good stuff!

the classic erma bombeck example imho...
 

speedtaco

Senior Member
Messages
913
I actually gigged it a couple of weeks ago Rusty, but you make a good point. I really liked the sound, and will probably use it as a backup. It does sound greAt in my tv room though!
 

mgreene888

Member
Messages
6
Just out of curiosity, I'm wondering where you guys have your settings on your Princetons (As far as the treble and bass). I have my bass on zero and my treble around 5.5. Of all my Fender amps that's the only one that I keep the settings like that. All the others have the bass up pretty high

I have a 10uf bypass cap on the first triode - this simple mod tames the bass to good effect on this amp. My settings are treble 6 and bass 5 with a Tele. My typical Fender settings are 5-4-3 T-M-B. I had planned to do a mid pot mod on this amp but with the 10uf cap and the mid heavy orange drops it doesnt need it.

Mike
 




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