Princeton Reverb Kit for an absolute Newbie?

[azatplayer]

Actually the cheaPest celestions on eBay are from a seller in singapore!

[angelodp]

Very doable as a first build. There are numerous pics floating around to get a good sense of lead dress and components. Its a well known circuit so it should go well.

Have fun
Ange

PS start building your bulb tester

[TheHandsomeOrk]

While I am flattered that some think I know something about a princeton. I know nothing about the kits available and would have to defer to someone who has actual experience with the various kits.

A few thoughts that come to mind.

1. Solid pine ,finger jointed cabinet.
2. even though the originals had a particle board baffle I would use a 1/2" baltic birch ply baffle.
3. Transformers- get the very best you can. The output is the most important. You might like a Deluxe reverb OT for better bottom end. Maybe Heyboer or Mercury, I don't care for the Magnetic Component ones I have tried.
4. If you are going to use a 12" speaker, check out the Eminence Wizard. I just heard one and it was very nice. Celestions work but don't sound very Fendery.
5. use a 9 series, Medium decay reverb pan. However, I don't like the sound of any of the new pans.
6. a good tweak is to raise the value of the middle resistor from 6.8K to 10K.
7. Use Carbon Comp Resistors, even the 470 ohm screen resistors, use screen resistors even if the schematic does not show them, I use 1.5K grid resistors too. While neither are necessary , they smooth things out and cause no sonic problems. I find the 1W 470 ohm screens can protect the OT if a tube fails. So use 1W not 5W. It is much easier to replace a burned resistor than the OT or speaker.
8. Use Polyester film and foil caps, not Polypropylene. Maybe the new Sozo Blue ones.
9. for a squishy tone try a 5y3 instead of the gz34, in between use a 5u4 rectifier.
10. If you are going to use a longtailed pair phase invertor then just build a Deluxe reverb, because that is what you are building. personally I like the sound of the Cathodyne PI.

If you can build an express I think you can build a Princeton reverb, The layout is different. A bit more complex due to the Reverb and Vibrato circuits.

Good luck and happy soldering.

+1

In most Princetons, the limiting factor in power output is that the phase
inverter starts clipping before the 6V6s. Once the PI clips, there is nothing
left to push the 6V6s any harder. The tweak simply gives the PI a bit more dynamic headroom so that the 6V6s clip first. You simply move the B+ feed for the PI up one notch on the power supply voltage divider. Give it more voltage to work with, it's dynamic headroom increases, and now you can drive the 6V6s all the way. Leave the B+ feed for the remainder of the preamp stages alone. Move only the PI. Up one step.
The voltages in the Princeton are a bit lower than in it's bigger brothers. Yet it uses the identical circuit to drive the reverb pan. The lower voltages result in a lower drive level to the pan. Reduce the value of the 12AT7 cathode bias resistor from the nominal 2.2k to 1.8k. Running the tube at slightly higher current gives a little more drive and livens up the reverb a bit. You may like it or not.
Keep it from farting out by reducing the value of the
coupling cap feeding the input of the PI. That split load PI circuit topology
has a VERY high input impedance (several megohms) since the grid leak resistor is returned to essentially half the load (in the cathode leg), which follows the signal. That very high input impedance along with the stock input cap value result in lots of low end crap getting through which you don't need. I recommend using 1/4 the stock value. cleans up the low end fartiness with no loss in "real" low end tone.

[hendrixclaps]

Thanks for the advice guys. Yea i would like more headroom cause im kind of a clean tone guy.

I think speakers are the cheapest cos not many people do much amp mods here. mostly just pedal building and mods since those are easier to get parts.

[tubeswell]

FWIW my 'before' and 'after' threads of my Weber 6A14 (BFPR clone) kit experience last year (starting the year before last)

http://music-electronics-forum.com/t15349/

http://music-electronics-forum.com/t20860/

There was also another thread there where I was mouthing off about some of the stock parts quality (like the crappy plastic asian-rim lamp-holder, and if you are in a euro-voltage country, I would consider getting a better grade PT than the stock Weber one. There are a few reports of the smaller US-made 50Hz iron not lasting much past 12-months). But what the heck, it was a cheap enough kit. Actually it was quite good value for money, and once I had it all troubleshot it is a keeper. What's more I love the Weber speakers (I even scored a 2nd Sig12S and put in in a 1x12 extn cab that I use with the combo. - sounds awesome).

But not necessarily for a beginner IMHO. If you strike problems, it could get frustrating real fast. I have a few builds under my belt, so I knew the value of persistence, and I was experienced enough to be able to solve most of the issues myself (eventually). But I did have more than one 'hair pulling' moment, and it took me a little while (read "a few months") to get it all straightened out.

[Lonely Raven]

I love Weber speakers, and I enjoyed chatting with Ted back in the day...but those parts piss me off. I build a BF Champ clone with transformers I scored off eBay (real '64 BF Champ PT and OT someone was parting out!), and gathered the rest of the parts from Weber. I had two volume pots die in no time, and two electrolytic caps die in the first two years. I've since swapped out all the pots with Alpha and replaced the electrolytics with Sprague and the amp has been one of my favorites.

Great MP3 you have there Tubeswell.

[Richie]

I'm going to throw this out there and hope it helps,might be long winded for a small fix. But i want to explain how it came about. And i have never seen anyone else mention it.

I have been repairing quite a few Princeton reverbs and i found something while looking at al the forums for people having the same type problems.
This is very simple and it will change the amp to what it is supposed to be.

I see alot of mods etc to cure the problems. Some amps may have them,some may not. Just like a JCM 800. Some of those can be quiet,some can have noise problems,and be the exact circut.

But,back to the Princeton reverb. I don't know if over the years this was a mistake on the drawing,or overlooked or if it was intended to be that way.

But i see alot of people build these amps, and make them exact to the layout. They have problems of exactly what people on many boards try to get fixed.
I had one to rebuild that was having the same problems.

Look below at the princeton models. I think all the models but one will open when you get to the page .
And only one model was ever shown to have the parts that are missing from all the others.
http://www.ampwares.com/amp.asp?id=74

http://www.ampwares.com/amp.asp?id=76

The Blackface and Silverface reverbs.

On most fender reverb circuits there is a 220k resistor that goes to ground from the 470k junction. A voltage divider of sorts.
The wire feeds to the tube from the 470k.
On the Princeton Reverb the 220k is not show, or is missing.

Here is what i did on this one.

I put a piece of shielded cable from the 470k.
grounded shield at the board side.
Some use a FB from the tail of the cathode. Be sure to ground the shield on the ground side of this. Which is on the other side of a 47ohm resistor.
Its a longer piece to get there,so use some insulation or piece of heat shrink over the shield ground. Leave a small spot to solder one lead of the 220k that goes to ground.

Then install the 220k Off the 470k junction. And tie the ground side of the 220k to the shield,makes it short and easy.
And the last thing Andy Fuch brought up. Put a 500pf cap between the cathode and plate pin 1 and 3 on the reverb return tube 12ax7.

THATS IT.. done.!

Now what you have is an amp that stays much cleaner,doesn't have the buzz,splat crackle when turned up or hit a hard note or chord.
The amp will have more headroom,stay alot cleaner. The tubes won't seem so microphonic.

The other things mentioned are also great ideas. The upgrade of a good speaker. And use the standard value on the 6v6s for added 1.5k grid resistors and add 470ohm screen grids..

Maybe someone can draw up a nice drawing to show the changes or things added. I'm not much on drawing.

Maybe someone will try it in there amp and report.

[angelodp]

Richie, that is great info.

Thanks

[M Fowler]

Richie thanks for the PM and posting this as well.

Mark

[Richie]

Your welcome.

[telentubes]

Thanks for all that info. A new BFPR build is in the near future for me, and I'm really grateful for these suggestions. It will make a nice amp even better.

[Structo]

Wrong

[billyz]

I'm going to throw this out there and hope it helps,might be long winded for a small fix. But i want to explain how it came about. And i have never seen anyone else mention it.

I have been repairing quite a few Princeton reverbs and i found something while looking at al the forums for people having the same type problems.
This is very simple and it will change the amp to what it is supposed to be.

I see alot of mods etc to cure the problems. Some amps may have them,some may not. Just like a JCM 800. Some of those can be quiet,some can have noise problems,and be the exact circut.

But,back to the Princeton reverb. I don't know if over the years this was a mistake on the drawing,or overlooked or if it was intended to be that way.

But i see alot of people build these amps, and make them exact to the layout. They have problems of exactly what people on many boards try to get fixed.
I had one to rebuild that was having the same problems.

Look below at the princeton models. I think all the models but one will open when you get to the page .
And only one model was ever shown to have the parts that are missing from all the others.
http://www.ampwares.com/amp.asp?id=74

http://www.ampwares.com/amp.asp?id=76

The Blackface and Silverface reverbs.

On most fender reverb circuits there is a 220k resistor that goes to ground from the 470k junction. A voltage divider of sorts.
The wire feeds to the tube from the 470k.
On the Princeton Reverb the 220k is not show, or is missing.

Here is what i did on this one.

I put a piece of shielded cable from the 470k.
grounded shield at the board side.
Some use a FB from the tail of the cathode. Be sure to ground the shield on the ground side of this. Which is on the other side of a 47ohm resistor.
Its a longer piece to get there,so use some insulation or piece of heat shrink over the shield ground. Leave a small spot to solder one lead of the 220k that goes to ground.

Then install the 220k Off the 470k junction. And tie the ground side of the 220k to the shield,makes it short and easy.
And the last thing Andy Fuch brought up. Put a 500pf cap between the cathode and plate pin 1 and 3 on the reverb return tube 12ax7.

THATS IT.. done.!

Now what you have is an amp that stays much cleaner,doesn't have the buzz,splat crackle when turned up or hit a hard note or chord.
The amp will have more headroom,stay alot cleaner. The tubes won't seem so microphonic.

The other things mentioned are also great ideas. The upgrade of a good speaker. And use the standard value on the 6v6s for added 1.5k grid resistors and add 470ohm screen grids..

Maybe someone can draw up a nice drawing to show the changes or things added. I'm not much on drawing.

Maybe someone will try it in there amp and report.

That's a good one Richie. I will have to take a good look at my favorite Princeton rev and see if the 220K is there. Because everyone raves about the reverb in that one. It still sounded better with an Accutronic 9 series med decay pan though.

[Firestorm]

FWIW, I've never seen an original Princeton Reverb that has the 220K in the mixing stage grid circuit. I've always assumed its omission was deliberate since the PR has no PI gain and Fender compensated by boosting the signal into the third stage. I'd be afraid that with the 220K in place you wouldn't have enough signal to overdrive the 6V6s. (There is an issue with that, which Merlin B covers. His fix for the "blatty" sound is a large grid stop at the input to the PI).

Reverb tweaks are all pretty simple and reversible: run the 12AT7 with an unbypassed cathode 680R like on later silverfaces. I don't think this sounds so great (YMMV). 2000pF across the reverb pan return; this is inoffensive. 560pF between the 12AT7s plate and cathode; I like this.

But the very best sounding Princeton Reverb I've ever heard had a Jensen C10N speaker. It's way overkill from a power handling standpoint and I have no idea where you'd find the equivalent (we just happened to have it lying around), but it made a huge difference in both the clean and overdriven sound. If you have a copy of the second Norah Jones album, all the electric guitar tracks (well, all three or four of them) are through that amp.

[Richie]

So something like this?

the ground is on the other side of the 47ohm

the part you have it tied to is part of the FB circuit.