transformers for a 30-40 watt princeton reverb

[Shack]

Is there any out there that would provide what id need for that kind of power and fit in the chassis?

Also, what would I need to modify to make that happen....I already got the 12 inch speaker part, but thinking about filtering and bias pot.....cause would need 6L6 tubes, and possibly a SS rectifier to get what I seek.

want to keep rest of amp the same, if possible, as I have the chassis and cab ready to go. just looking for ideas.

[sluckey]

6L6s and super reverb iron

[p2pAmps]

6L6s and super reverb iron

What he said...  But is it really a Princeton anymore with iron that big? 

I used a standard PT and a Deluxe OT in mine and very happy.

[uki]

6L6s and super reverb iron

What he said...  But is it really a Princeton anymore with iron that big? 

I used a standard PT and a Deluxe OT in mine and very happy.

How does the iron effect the result that much ? What is the difference in those 2 in particular, does it change a lot the tone ?

[DummyLoad]

single channel & cathodyne PI make it NOT AB763 et-al. you will need CF or MOSFET source follower to do bias vary trem on 6L6 output stage: not recommended though. see this plan if you must have princeton trem.

basically, you'll have a somewhat louder and heavier PR. pass the spinach popeye. :[

--pete

[HotBluePlates]

6L6s and super reverb iron

Expanding what Sluckey said, 30-40w is 2x 6L6 or 4x 6V6. The iron is the same in each case because power output is only dependent on voltage current & impedance.

What is the difference in those 2 in particular, does it change a lot the tone ?

mscaggs is saying he uses a Deluxe Reverb OT for more power. A Princeton OT is 8kΩ while the Deluxe is 6kΩ or 6.6kΩ. With the same supply voltage, the lower OT impedance allows bigger plate current swings, times same plate voltage swings = increased output power from ~14-15w up to ~20-22w.

[jjasilli]

want to keep rest of amp the same, if possible, as I have the chassis and cab ready to go. just looking for ideas.

Is this a standard cab with baffle cut out for 12" speaker?  If yes, it might be hard to fit bigger iron with the larger speaker.  (one solution i a supplemental chassis for the iron.)

[Fresh_Start]

What is the practical goal of "more power"?

Need a lot more volume before onset of distortion for gigging?  Or just want cleaner amp?  Or stiffer, tighter sound and feel?

That answer may help with 6V6 plus Deluxe OT vs. 6L6 with bigger PT and OT and maybe solid state rectification (higher B+).  A choke, bigger filter caps and power rail tweaks might help get you where you want to be - provided you don't expect it to be a Princeton Reverb anymore. Just a cool amp...

Respectfully,
Chip

[tdvt]

mscaggs is saying he uses a Deluxe Reverb OT for more power. A Princeton OT is 8kΩ while the Deluxe is 6kΩ or 6.6kΩ. With the same supply voltage, the lower OT impedance allows bigger plate current swings, times same plate voltage swings = increased output power from ~14-15w up to ~20-22w.

Looking at both BF schematics; same output tubes, same bias, same B+, but different driver/PI, grid resistors....... what other parameters change the equation to have a lower impedance (= more watts)?

[mresistor]

To echo others here - I built my Hoffman Princeton Reverb using a Deluxe Reverb OT and I can't even imagine what it would be like any louder. It's one pretty potent and toneful amp as it is; and running through a 2 x 12 cab. But I also used David Allens TP25 which is oversize for the build.


DL   I built my PR to be able to use EL34s/6L6s  are you saying the Trem will not work?  Why not? Because of the change in bias voltage?

[Ed_Chambley]

To echo others here - I built my Hoffman Princeton Reverb using a Deluxe Reverb OT and I can't even imagine what it would be like any louder. It's one pretty potent and toneful amp as it is; and running through a 2 x 12 cab. But I also used David Allens TP25 which is oversize for the build.


DL   I built my PR to be able to use EL34s/6L6s  are you saying the Trem will not work?  Why not? Because of the change in bias voltage?

I have a PR with a Deluxe OT and it has a nice tremolo using 6L6 tubes.  I have read many posts where guys have trouble getting the trem to swing using the AA1164 circuit.  I do not know exactly why I have not had any problems, but mine has dual bias which I don't see as benefitting.  Just thought I would let you know.

There is a LED modification that can be done. I think that is what DL linked to if you scroll down to the bottom of the PDF.  Most seem to tend to bias on the cold side even when using 6V6.

I agree, I have one of mine in a 2, 10's cab and it is easily in BF Deluxe volume territory.  With 6L6's plugged in I get a nice jump in headroom.

[Ed_Chambley]

6L6s and super reverb iron

What he said...  But is it really a Princeton anymore with iron that big? 

I used a standard PT and a Deluxe OT in mine and very happy.

How does the iron effect the result that much ? What is the difference in those 2 in particular, does it change a lot the tone ?

More current at higher voltages will enable the use of larger tubes.  This is from the larger Power Transformer.  Begin to study tube data sheets which show how the tube will perform at differently.  Your question has a lot of variables which cannot possibly covered in one post.

Sure the tone will change.  Generally speaking a larger Output Transformer will produce a wider Hz range cleanly.  When changing the Princeton Output Transformer with a larger one like a Deluxe, the transformer will pass more low end cleanly.  You will also get more clean headroom, but it is no longer the same amp.

[Shack]

Ok, heres the story,lol...

Last year I built a 5e3....awesome, except that when I tried to play it with band, it wasnt loud enough at all. Well, I had already ordered the chassis for the PR, and my friend built me an awesome cab....PR dimensions except I asked him to make it 1 inch taller and include a 12 inch baffle. This amp is too cool to be a practice amp, and since I havent bought iron yet, I thought id ask here before I built yet another real cool amp that I cant use with band.

Since I want the PR tremolo and am missing a tube stage for a DR power section, I thought it would be cool to build a super PR.....and you guys are the ultimate place to ask for help with this stuff :P

[HotBluePlates]

mscaggs is saying he uses a Deluxe Reverb OT for more power. A Princeton OT is 8kΩ while the Deluxe is 6kΩ or 6.6kΩ. With the same supply voltage, the lower OT impedance allows bigger plate current swings, times same plate voltage swings = increased output power from ~14-15w up to ~20-22w.

Looking at both BF schematics; same output tubes, same bias, same B+, but different driver/PI, grid resistors....... what other parameters change the equation to have a lower impedance (= more watts)?

"Parameter that changes to have lower impedance" = Output Transformer Winding Ratio (Primary to Secondary).

 

• There are fewer turns on the primary, same load attached to the seocndary, which yields a lower reflected primary impedance.
• B+ voltage is the same, as is tube type. The tube has a minimum B+ voltage which must exist from plate-to-cathode at peak plate current
• Same Voltage (say 380v net of the minimum plate-to-cathode voltage) times lower OT Primary Z = Higher Peak Current
• Higher Current * Same Voltage = Higher Power Output

Ignore tube type for a moment and consider Princeton Reverb vs. Deluxe Reverb vs. Super Reverb... All are roughly the same B+. Princeton OT primary is 8kΩ, Deluxe OT primary is 6.6kΩ, Super Reverb OT primary is 4kΩ. Power outputs are typically stated as 15w for Princeton, 22w for Deluxe, 40w for Super. See the pattern?

At the end of the day, the PT, power supply and OT primary impedance dictate the maximum power you can push to a speaker. The you need a tube (or tubes) which can swing the current implied by the power supply voltage & OT impedance to allow the maximum power output to be achieved. And even if you have all those pieces, you can hamstring the output tubes to be unable to swing all the current they otherwise might, and have the output stage perform well below its full capability (power reduction schemes, anyone?).

You shouldn't, but probably could cobble together 80 12AU7's as an output section to deliver 30w to a speaker load... Unfortunately, there are a lot of bad shortcuts/"rules" popularized which hinder wider understanding of this stuff. The "rules" are often based on observations of "typical use" in different guitar amps but often give an incorrect rationale for why it's a "rule".

[Shack]

I have been planning on buying the DR trannys from Allen for it, just wanted to see what options I have, this is gonna be an awesome amp.  I dont have a big enough wallet to build all my wants and want to use an amp I build instead of my workhorse HRD that I use now.

[Shack]

mscaggs is saying he uses a Deluxe Reverb OT for more power. A Princeton OT is 8kΩ while the Deluxe is 6kΩ or 6.6kΩ. With the same supply voltage, the lower OT impedance allows bigger plate current swings, times same plate voltage swings = increased output power from ~14-15w up to ~20-22w.

Looking at both BF schematics; same output tubes, same bias, same B+, but different driver/PI, grid resistors....... what other parameters change the equation to have a lower impedance (= more watts)?

"Parameter that changes to have lower impedance" = Output Transformer Winding Ratio (Primary to Secondary).

 

• There are fewer turns on the primary, same load attached to the seocndary, which yields a lower reflected primary impedance.
• B+ voltage is the same, as is tube type. The tube has a minimum B+ voltage which must exist from plate-to-cathode at peak plate current
• Same Voltage (say 380v net of the minimum plate-to-cathode voltage) times lower OT Primary Z = Higher Peak Current
• Higher Current * Same Voltage = Higher Power Output

Ignore tube type for a moment and consider Princeton Reverb vs. Deluxe Reverb vs. Super Reverb... All are roughly the same B+. Princeton OT primary is 8kΩ, Deluxe OT primary is 6.6kΩ, Super Reverb OT primary is 4kΩ. Power outputs are typically stated as 15w for Princeton, 22w for Deluxe, 40w for Super. See the pattern?

At the end of the day, the PT, power supply and OT primary impedance dictate the maximum power you can push to a speaker. The you need a tube (or tubes) which can swing the current implied by the power supply voltage & OT impedance to allow the maximum power output to be achieved. And even if you have all those pieces, you can hamstring the output tubes to be unable to swing all the current they otherwise might, and have the output stage perform well below its full capability (power reduction schemes, anyone?).

You shouldn't, but probably could cobble together 80 12AU7's as an output section to deliver 30w to a speaker load... Unfortunately, there are a lot of bad shortcuts/"rules" popularized which hinder wider understanding of this stuff. The "rules" are often based on observations of "typical use" in different guitar amps but often give an incorrect rationale for why it's a "rule".

I suppose this is the stuff I dont quite understand....I have studied fender schematics for the last year and so many amps are the same, and the schematics dont educate you on these differences.

I would go forward with the build with the allen DR trannys and 6v6, just want this amp to have the clean headroom to be heard in the mix. Hot rod deluxe is a monster but dont sound like the old fenders and I cant afford to start a new build , like a Brown Vibroverb, which uses the same tremolo circuit with 6L6 .....


I do appreciate the education I get when I ask questions here, the knowledge is astounding, and sometimes overwhelming

[Fresh_Start]

You can put 6L6 power tubes in this amp and get more power output with more headroom. Deluxe Reverb 6.6K primary on the OT will help accommodate 6L6s even if 4K is optimal for maximum output. However, the OT and PT both need to have the current/volt amp capacity to handle the more powerful output tubes. And don't forget heater current. And different bias voltages. You may need a bigger bias adjustment pot to get range to cover 6V6s and 6L6s.

I've built a couple of Princeton Reverbs and one Suoer Reverb. The cathode follower/buffer in the tremolo circuit sure didn't hurt with 6L6s, but you can easily use a MOSFET there (Search).


I also included several of the tremolo strengthening tweaks covered in the Archives here for the Super Reverb build. I had more trouble needing to bias the Princetons cold enough for the trem to work than I did with the Super.

Bottom line:  Sluckey was dead on but you may not want to go all the way with a Suoer Reverb OT. Either way, with an efficient 12" speaker, your amp will be LOUD!

Chip

[mresistor]

- also use JJ 6V6 in conjunction with the DR OT   

[tdvt]

mscaggs is saying he uses a Deluxe Reverb OT for more power. A Princeton OT is 8kΩ while the Deluxe is 6kΩ or 6.6kΩ. With the same supply voltage, the lower OT impedance allows bigger plate current swings, times same plate voltage swings = increased output power from ~14-15w up to ~20-22w


"Parameter that changes to have lower impedance" = Output Transformer Winding Ratio (Primary to Secondary).

 

• There are fewer turns on the primary, same load attached to the seocndary, which yields a lower reflected primary impedance.
• B+ voltage is the same, as is tube type. The tube has a minimum B+ voltage which must exist from plate-to-cathode at peak plate current
• Same Voltage (say 380v net of the minimum plate-to-cathode voltage) times lower OT Primary Z = Higher Peak Current
• Higher Current * Same Voltage = Higher Power Output

Ignore tube type for a moment and consider Princeton Reverb vs. Deluxe Reverb vs. Super Reverb... All are roughly the same B+. Princeton OT primary is 8kΩ, Deluxe OT primary is 6.6kΩ, Super Reverb OT primary is 4kΩ. Power outputs are typically stated as 15w for Princeton, 22w for Deluxe, 40w for Super. See the pattern?

I knew that a Deluxe & Princeton use the same output tubes but had attributed the higher wattage (Deluxe) to the different driver (higher input signal?) & that maybe the voltage was higher (never compared voltage until now).

What I didn't realize/consider was that the OT impedance is/would be different, as I assumed the 6V6's had a more specific requirement, not a functional range.

It sounds (no pun intended) like Leo could have put the same bigger OT in the both amps & had the same (nearly?) output ratings. But probably chose to differentiate the Princeton as a "student" model & save a little $$ on the OT as the same time.   

[Willabe]

It sounds (no pun intended) like Leo could have put the same bigger OT in the both amps & had the same (nearly?) output ratings. But probably chose to differentiate the Princeton as a "student" model & save a little $$ on the OT as the same time.

Yes, that's probably what he did.

But that's good for us because we now have to little bit different amps from him sound wise. 

[Shack]

I have learned the same thing.....so thats what im gonna do,....going to put in an Allen PT with the current ratings to handle 6L6 or even EL34.....and use their OT for a DR.

I didnt realize while reading over all the schematics that the B+ was so close on these amps, and the OT made a difference on power. 

Im gonna use the iron I had on hand for a PR to build a vibrochamp into an old Fender SS amp for my other guitarist to use as a practice amp, should be cool too.

[alerich]

What he said...  But is it really a Princeton anymore with iron that big? 

No, not really. A Princeton is a Princeton PT and OT, 6V6's and 1x10" speaker. Even swapping the speaker and baffle for a 12" makes it no longer really a Princeton. That single 10" speaker is part of the Princeton tone. One may like it better with a 12" speaker but it becomes a different animal then. I swapped out my PRRI OT for one of those BillM OT's and while it sounded ok, it didn't sound like a Princeton anymore so I put it back.

But then again... I did the Stokes mod and added another 22uf cap in parallel to the first filter in my PRRI so I don't have any room to talk. 

[Shack]

well since ive never played a PR, I am just building an amp, and am going for a sound, not trying to recreate anything. just want a classic fender tone at a level that can be heard with an animal of a band .....oh, and have fun making it :)

[alerich]

well since ive never played a PR, I am just building an amp, and am going for a sound, not trying to recreate anything. just want a classic fender tone at a level that can be heard with an animal of a band .....oh, and have fun making it :)

Most classic Fender amps are built using the same basic circuits. Wattage and speaker setups are the main differences. Based on the wattage you are looking for I would start with the Super Reverb circuit. Since you are planning to use a PR chassis that eliminates the need for the normal channel components since you don't have that feature on the faceplate. Do you want/need reverb? You can leave it out, too if you won't need it. I never use the reverb on my PR. I prefer a touch of slap back delay. Design the circuit around only what you need or will use and exclude the stuff you don't need.

You said you want the PR tremolo. Did you mean the actual PR style tremolo or just tremolo, in general? The PR uses the bias vary tremolo circuit. I like the sound of it but it can be tricky to get it where you want. The hotter you set the tube bias the less impact the tremolo has. It's a balancing act. All of the larger Fender amps use the roach based trem circuit. I prefer the sound of the bias vary circuit but the roach circuit isn't beholden to how hot you set the power tube bias.

You have mentioned that clean headroom is important as is plenty of volume. I think that means you're likely going to need a duet of 6L6 output tubes. The logical choice for iron would be the Super Reverb iron with a more modern OT that has 4-8-16 ohm taps.

Since you have already purchased and would like to use a PR chassis and cabinet you'll need to make sure that the physically larger transformers will fit. They probably will with a little creativity. I stuffed a 50W JCM800 into a combo that once housed a solid state practice amp with a 8" speaker. It was a tight fit but it works. I had to install a small computer fan to manage the temperature. But - I left the speaker out. Had to. No room. Trying to fit the larger transformers in the combo while using the 12" speaker you plan to use may be an issue. You said you had the cabinet made 1" taller. That may help. The upside is you're pretty much in for the iron anyway for the wattage and headroom you desire so you can go ahead and order them. If it doesn't all fit you may have to find another chassis and cabinet for the project.

Since your chassis already has a spot for a tube rectifier I'd plan on wiring it for one. You can always insert a solid state plugin, if you like - that should give you a tad more operating voltage. The small increase may not be really noticeable for a 45-50 watt amp. It's nice to have both options.

 

[Shack]

thx for all the replies, gives me a bit to think about. I do want to keep the reverb and bias tremolo, so that factors in my decision. I did manage to plan the cabinet and speaker baffle to hold bigger iron, so think thats not an issue.

Will have to study the difference between a PR and brown Vibroverb tremolo I guess.....will definitely keep the forum posted.

I know it will turn out good, because of the knowledge in this forum :)