Switchable Princeton/Tweed Deluxe?

I looked at the schematics, it looks like the only difference between a blackface Princeton Amp (no reverb) and a 5E3 is the tone stack, bias, preamp tube, and rectifier tube. If I made a Princeton without the tremolo and added switches to bypass the tone stack and change the bias between cathode and fixed, wouldn't that let me get both tweed and blackface tones from the same amp?

My apologies....I had not had my tea for the morning...still asleep.

Maybe I misunderstood you, but I was looking at the 5E3, not the 5F1.

Yes the BF princeton (sans tremolo) is like the 'blackface evolution' of the tweed deluxe, but with a single channel input leading to your typical BF Treble/Bass tonestack, and fixed bias output tubes and BF style NFB loop contributing to the 'tightness' of the BF princeton. The BF princeton power supply is also different - the GZ34 makes the B+ much higher and the RC supply string is less spongy.

Also, the interactivity of the vol/tone controls in a 5E3 is quite different to the BF style single channel with TB tonestack tho', and you may well be able to get there with a morass of switches, if you opt to use the trem triode for another input stage.

And having the 12AY7 in V1 in the 5E3 is much bluesier.

So there are quite a few differences when you start to get into it.

Yes the BF princeton (sans tremolo) is like the 'blackface evolution' of the tweed deluxe, but with a single channel input leading to your typical BF Treble/Bass tonestack, and fixed bias output tubes and BF style NFB loop contributing to the 'tightness' of the BF princeton. The BF princeton power supply is also different - the GZ34 makes the B+ much higher and the RC supply string is less spongy.

Also, the interactivity of the vol/tone controls in a 5E3 is quite different to the BF style single channel with TB tonestack tho', and you may well be able to get there with a morass of switches, if you opt to use the trem triode for another input stage.
I'm going to use a solid state rectifier with a "sag" control if it doesn't change the sound too much. How much different would the amp sound? I know that would give it more headroom, that's a good thing with the 5E3. It will have a PPIMV for when I need distortion.

I also want to keep it a single channel amp, I want it to be simple and I don't want too many switches. Two is enough, and I might even start with a 5E3 with a switch to add the tone stack. I have a 50k pot that was also used as the power switch on a 60s solid state amp, I can use that for the mid pot and that will switch the tone stack out.

A 2.7k negative feedback resistor is a very small difference from no negative feedback. When I was working on my Champion 600, I tried no NFB, 2.7k, 22k, and 47k. I liked the clean sound better without it, so I'll leave it off this one too. If I think it sounds too harsh I can add it later.

Edit: I read that a solid state rectifier won't work well in a Princeton or tweed Deluxe. Should I use a 5Y3? A lot of people like them in their PR.

Every little change will have a little effect on the sound. Taken by themselves, such as the NFB, they do not sound like much. But by the time you throw in a lot of changes a meatloaf no longer tastes like the burger done on the barbeque. The 5E3 volume and tone circuit is different than the 6G3 circuit even though they use the same parts, just hooked up backwards from each other. How much does it change the character of the amp? Wish I could tell you, I cooked up a circuit to switch between the two to determine the differences but have not found the time to try it out yet,

Now as far as an amp that can go from 5E3 to Princeton in a matter of two switches, I would think it possible. The difference in power supply voltage could be included by going to a four pole switch on the PA bias/feedback switch. The circuit is still in the conceptual stage, hope to get it going in a few weeks.

http://i406.photobucket.com/albums/pp142/printer2_photo/guitar%20amp/5E3PrincetonRev0720.jpg

Every little change will have a little effect on the sound. Taken by themselves, such as the NFB, they do not sound like much. But by the time you throw in a lot of changes a meatloaf no longer tastes like the burger done on the barbeque. The 5E3 volume and tone circuit is different than the 6G3 circuit even though they use the same parts, just hooked up backwards from each other. How much does it change the character of the amp? Wish I could tell you, I cooked up a circuit to switch between the two to determine the differences but have not found the time to try it out yet,

Now as far as an amp that can go from 5E3 to Princeton in a matter of two switches, I would think it possible. The difference in power supply voltage could be included by going to a four pole switch on the PA bias/feedback switch. The circuit is still in the conceptual stage, hope to get it going in a few weeks.

http://i406.photobucket.com/albums/pp142/printer2_photo/guitar%20amp/5E3PrincetonRev0720.jpg

I think that's exactly what I'm looking for.

Forgot to mention, the above uses dual pots for the volume and tone. Just looked back and saw that you were thinking of a single channel amp, that can be done easier.

http://i406.photobucket.com/albums/pp142/printer2_photo/guitar%20amp/Tabletop3schematic.jpg

Just stick a gain stage in the BF tone stack loop after the stack.

I think that's exactly what I'm looking for.

Might be a little tricky to make. How is your amp building experience?

Might be a little tricky to make. How is your amp building experience?
I've never built an amp. I turned a Champion 600 into a GA-5 and rewired the jack and pots, but that's it. So would this be too complicated? I don't want tremolo or reverb and I can make it cathode biased with no fixed bias switch.

Forgot to mention, the above uses dual pots for the volume and tone. Just looked back and saw that you were thinking of a single channel amp, that can be done easier.

http://i406.photobucket.com/albums/pp142/printer2_photo/guitar%20amp/Tabletop3schematic.jpg

Just stick a gain stage in the BF tone stack loop after the stack.

That one has a lot of switches! Would it really be worth the extra work for the switchable cathode bypass caps? What is the top part of the tone stack switch? And the switch after the phase inverter?

I should have explained this one better. I was really trying to point out the tone stack part if you wanted a Tweed - BF combination in one amp. The switched cathode bias in the preamp stages were just for me to see how changing the circuit would sound. The tone stack is bypassed in the middle position and the top one has the frequency response shaped more toward a higher gain sound. The switch after the PI was so I could run the amp as a Single Ended amp, the amp is biased Class A so I could do that.

It all depends on what you are trying to get. If you want an amp that has the exact characteristics of either amp you have to do some creative circuitry. Now if you wanted a BF sounding amp with a Tweed option I would do the BF circuit and use a tone lift switch on the tone stack ground. This will pretty much take out the tone stack and let the signal through to the next stage. Using a Tweed tone knob on the volume pot gives you the tweed flavor, if you decide to keep it in the circuit all the time it can be thought of as a adjustable treble bypass switch. The switching in and out of the tone stack as I showed above is only really needed if you are using dual pots in order not to have the tone extra control knob.

I found I had more than enough gain with this circuit to get the BF mode to distort. Tweed position it has more than enough for me.

http://i406.photobucket.com/albums/pp142/printer2_photo/BFPrincetonTweed.jpg

I have a sligthly different spin on what to do that might be interesting. Instead of two channels like the 5E3 just use one of the preamp channels for the 5E3 and have it pass through its tone and vol section. Us the other channel to emulate the princeton with its tone section.

The nonly left with switches for NFB and bias

Downside is you lose the interactivity between channels of the 5e3 but many dont use this feature. Also you then have to pick what your preamp tube will be (or you can add two tube sockets and have totally different preamps for each amp).

Ive never played a guitar thru the blackface princeton...whats it like?

I have a sligthly different spin on what to do that might be interesting. Instead of two channels like the 5E3 just use one of the preamp channels for the 5E3 and have it pass through its tone and vol section. Us the other channel to emulate the princeton with its tone section.

The nonly left with switches for NFB and bias

Downside is you lose the interactivity between channels of the 5e3 but many dont use this feature. Also you then have to pick what your preamp tube will be (or you can add two tube sockets and have totally different preamps for each amp).

Ive never played a guitar thru the blackface princeton...whats it like?
I thought about that too, but I think a simple switch would be easier than a whole second channel. I can use push/pull pots for the switches so it won't look any different than a Princeton. It will basically be a Princeton with a switch to bypass the tone stack, and I might add another switch or two for the bias and NFB.

What if I made a Princeton, but put the tone stack after the second gain stage like a Bassman or Marshall? Then I could use a 3 way switch between the blackface and Bassman tone stacks and no tone stack.

It should still sound like a Princeton when the blackface tone stack is switched on, but it would break up quicker because there are 2 gain stages before the tone stack, so it's cutting less gain than if it was after the first stage. It should also be smoother, the tone knobs can make it sound less harsh. Does that sound right?

I can leave out the bias switch, and a 2.7k NFB resistor doesn't do enough to add a switch for it. I don't really need it to sound exactly like either amp, just a good blackface sound and something like a tweed. There are so many different "tweed tones", it will probably sound like one of them.

funny you mentioned this. Bassman is my next project at some point. love that amp! but a combination amp that is part Bassman and part 5E3, that is a very attractive idea.

If I do that it would be a Bassman, Deluxe, and Princeton hybrid. Won't sound exactly like a Bassman, but should sound like a Princeton and close to the Deluxe. But it would be a lot of work for the first amp I build. I should probably start with something like a Champ, but I already have one.

From quite a while back, switches the tone stack before and after the second stage with a three pole switch. Also a tone stack defeat.

http://i406.photobucket.com/albums/pp142/printer2_photo/guitar%20amp/PrincetonSwitchedToneStack.jpg

Cool! Is that still only two switches?

Cool! Is that still only two switches?

Yes. Mind you the tone lift (defeat) switch on the bottom could be optional if you use a midrange pot instead of the 6.8k resistor. I just have it there to flatten out the response but you can do that with a three control tone stack. Really this is basically a Princeton with the addition of the three pole switch moving the stack around, and of course the tone lift switch.

I put a grid stopper in the cathodyne PI stage, would be a good idea to do that for the second stage also. I would not put too much faith in the values on the parts on the schematic, it was drawn up more to conceptualize the idea than anything else. I have this amp 75% done but have been side tracked with other ones. Should get back to it yet.