Princeton Reverb vs Deluxe Reverb clean output volume

[psychepool]

I made a princeton reverb clone.
It has Hammond 1760H output transformer. (the replacement for Deluxe Reverb : 6.6K 20W)
Bias can adjust. I set the 6v6 bias at 20mA. (Plate Voltage is about DC410v)

It sounds good. But I want to increase clean tone volume.

So I considering about make Deluxe Reverb.
But I can't sure about the Deluxe Reverb has louder clean tone volume.
I'm not say about crank up volume. Just want to know about clean tone volume.


My clone amp chassis has 4 9pin tube hole and 2 8pin tube hole.
So I want to make only reverb channel.
I don't use vibrato frequently.
So losing the vibrato circuit is not matter to me.


Please tell me the difference of clean volume between the Princeton Reverb and Deluxe Reverb.

[Stevem]

Back your output tube bias back to 17 or 18 ma and change out your PI output coupling caps to .022 uf.

[Leo_Gnardo]

Please tell me the difference of clean volume between the Princeton Reverb and Deluxe Reverb.

Not much.

I've seen both Princetons & Deluxes range generally from 13 to 19 watts at clip, depending on output tubes mostly. Of course higher power can be delivered from a larger power supply. Going to a solid state rectifier will buy you a couple more watts. But for a really noticeable difference two things will get you there. 1) Efficient speaker. I repaired a botch modified Princeton a couple years ago, put it back to stock. But it had a rare Altec 419 10" speaker in it. WOW did that amp sound good. Also weighed like a bowling ball and a half. Remember you can swap in a 12" baffle, Mojo generally has 'em ready to ship for a reasonable $65 or so last I checked. And there's lots of efficient speakers you can choose from. 12" Altec 417's a bit easier to find, or JBL K or D 120's. Lots other efficient speakers these days, look for 100 dB/ watt or more spec. Efficiency: make the most of what you got.

then B) more power. Not just a little. Double is only 3 dB louder, go for at least that. You'll have 6L6 output tubes, a bigger OT, probably a bigger PT too. Take a look at Allen Amplification's "Sweet Spot" and "Accomplice" amps, the higher power options are along the lines of where you want to go. Another little company Gries, offers an amp essentially along these lines, a double power Princeton. One of my customers has the Gries and it's been an excellent amp except for when its Mercury power transformer mysteriously self-destructed. Sized like a Deluxe, simple control set, no vibrato, about 35 watts with a pair of 6L6's. He's loaded it with a Warehouse speaker, he happens to like the tone.

Since you're custom building, think about making either separate head & cab, or a combo cab with closed back. You'll get a lot more low & mid oomph from your speaker in closed cabs, open back just throws away a lot of low end. Another option sort of in between, close up as much of the back as you practically can. I recently did this in a Twin Reverb, half inch oak ply, extra bracing, hole in the middle to stow the AC cable & pedal, an inch or so crevice at top for tube heat to escape. Noticeably more roar, no longer a loud plinky sounding amp.

[andyfromdenver]

need 5 9pin sockets for the LTP.

*edit, I see you would willingly nix the Trem. I'm out, can't advise such shenannigans *

[Craig B]

Been there! If the PR has enough volume for you but is too dirty to be usable, you can clean it up by increasing preamp and PI voltages. Moving the PI to the unused power supply node and decreasing the 18k resistors in the dropping string to 10k or even less will reduce distortion at high volume. I like to see 200 volts on the plates of the preamp tubes. Heresy to the many fans of the "PR sweet distortion at low volume" camp. The sound has a harder edge to it at low volume but sings when cranked. Reducing cathode caps on the preamp triodes to 4.7u also helps by cutting bass distortion. Fewer of those precious watts go to trying to produce power-sucking bass frequencies.
--Craig

[psychepool]

I thank all of you for your answers.

Stevem,

What results do occur due to the things you said?
Dosen't output volume also decreased by lowering the bias?
And why lowering the capacity of the PI coupling cap?
I know that coupling capacitance is related to the amount of bass.
I want to know the relationship between capacitance and clean tone volume.
And does the original tone will be changed?


Leo_Gnardo,

I made this amp with head type. So to change the speaker cabinet will not be a fundamental change.
I made very small head, so many specifications are designed very tight.
Already made it with solidstate rectifier for do not use rectifier tube.
Power transformer's current is also very tight. When I install 5881 tubes and apply higher bias, there's huge voltage drop.
The head cabinet and chassis is very tight too, no space for more large size transformers.
The core of my question was about whether to increase the clean volume without change the main hardware specfications.


andyfromdenver,

Yes. I don't use vibrato frequently. When I need vibrato, I will use stompbox tremolo.
I can give up the vibrato circuit if the deluxe reverb circuit makes more clean volume.


Craig B,

Thanks to good advice!

In fact, It is the thing that always I wondered.
What is the reason that this point does not connected with any tube plates?

It is temting advise that higher plate voltage with lowering the power supply resistance.
Have you experienced the result of lowering resistance?

I considered lowering cathode bypass cap but it's not for clean headroom. Just tonal reason.(Too much bass)
But if cuts the not-used bass frequency, will be get more not-distorted tone volume in useful frequency.
The word that Stevem said "change out PI coupling caps to .022uF" could be means this.

[Craig B]

The totally unsubstantiated rumor is that the unused power supply node in the Princeton Reverb was intended for the PI plate but allowed too much clean power and made the cheep PR a competitor to the more expensive DR. I like that story so I choose to believe it. Attached is the current schematic of my PR. Changing to the 4.7 uf cathode caps shaves off a tiny amount of the deepest bass--but it is enough to reduce distortion. The changes to the B+ dropping string helped too. I love the idea of partially closing the back of the cabinet--gotta try that on mine. I figure that anything that increases the bass output of the speaker allows me to turn down the bass control and use those watts for clean power elsewhere in the spectrum.
--Craig

[psychepool]

That's very interesting rumor.
Because the rumor, now the original circuit looks very imperfectly.

I expected you change the cathode cap only first stage, but you changed the all stage.
Is there a difference between changing only first stage and changing all stage?

And if lowering the power supply resistance makes more clean volume, Why you did not lower more like 10K or 1K? Why you choose only 15K?

[Craig B]

I originally used a 4.7uf cap on only the first triode. That did not remove enough of the low bass to reduce distortion so I also switched the next two triode cathode caps too. I could have used an even smaller cap on the first triode like Marshall amps do (.68uf) but found that I lost too much midbass to sound good.
I choose the 15k dropping resistor to the PI to give me the same voltage as the identical circuit from the Tweed Bandmaster 5E7. Perhaps someone with better theoretical knowledge and math skills can tell us if it is safe to have higher voltage on the PI cathode.
--Craig

[psychepool]

Thank you for your detailed discription.

I think about switching cathode cap by parallel (5uF+15uF) to use original tone.(use 3pdt switch)
I will consider about the dropping reisitor value about 10K or low.

Thanks anyway.

[jjman]

Has it been documented that a stock PR clips in the PI or preamp before the 6v6s? I know my DR clips in the 6v6s 1st so cleaning up or increasing voltages in its preamp or PI isn't going to provide more clean output from the speakers.

I know the PR has a cathodine PI which does not provide signal boosting but that doesn't automatically mean it has to clip 1st. But it could. Has anyone measured it? Is PR breakup all about the cathodine clipping?