Making a BF Princeton Reverb sound tweedish?

[Bluefinger]

Hi,

I am thinking about this: I'd like to build an amp that is small, yet efficient, has integrated reverb and bias tremolo, a nice tight bottom end and mellow tone. A 1x12 BF Princeton seems like a good place to start. With a Deluxe Reverb output tranny and mabe a GZ34 it would be plenty loud. Reverb and bias tremolo is there as well. The only thing I am concerned about is the BF frequency range ... i am used to tweed amps (Super, Pro, ...) and even if I install a mid pot instead of the fixed resistor, turning up the mids and turning down the treble does not make it a tweed amp. What would be a good way too get rid of those aggressive BF treble frequencies and to make the tone a bit smoother to get that tweedish kind of response? Would bigger coupling caps and different cathode resistors and caps do the trick or should I rather combine it with some kind of tweed preamp section? Any ideas how this could be done?

thanks!!!

[ThermionicScott]

Hi,

I am thinking about this: I'd like to build an amp that is small, yet efficient, has integrated reverb and bias tremolo, a nice tight bottom end and mellow tone. A 1x12 BF Princeton seems like a good place to start. With a Deluxe Reverb output tranny and mabe a GZ34 it would be plenty loud. Reverb and bias tremolo is there as well. The only thing I am concerned about is the BF frequency range ... i am used to tweed amps (Super, Pro, ...) and even if I install a mid pot instead of the fixed resistor, turning up the mids and turning down the treble does not make it a tweed amp. What would be a good way too get rid of those aggressive BF treble frequencies and to make the tone a bit smoother to get that tweedish kind of response? Would bigger coupling caps and different cathode resistors and caps do the trick or should I rather combine it with some kind of tweed preamp section? Any ideas how this could be done?

thanks!!!

Increasing coupling caps won't do it, but you could revoice the tone stack to be more like the 5F6A Bassman. Or go even further and change to a Vol/Tone circuit as seen on the 5F2A and a zillion other tweeds.

- Scott

[loudthud]

Kendrick's Tweed control is basically a 3Meg pot in series with a .01uF cap which bridges across the Treble cap to the center terminal of the Treble pot in the typical BlackFace tone stack. It fills in the Mid divit that is inherent in the BlackFace tone stack.

[cminor9]

I wonder if if might make more sense to build a tweed with the trem you want (5g9?) and add reverb? Gaze at fender schematics enough and you cannot help but notice that there is a lot more to it than changing out the tone stack. I'd think you could lift the reverb out of something like a brown vibroverb and drop into a tweed? Or maybe look at the brown face amps. Seems like a natural compromise between tweed and blackface.

[Bluefinger]

I thought about that too and I know I can't have it all. I do like manythinks about the Princeton .. it's got good efficiency, The reverb and trem sound great and the tight bottom end is what I am looking for in this build as well. I also want at least a bass/treble tone stack. There arecountless possibilities but I have to go for one. Mabe I could use a 5F4 preampsection in front of the reverb ... I don't know ...

[ThermionicScott]

You'd probably want to add a cathode follower if you want to use the 5E5A/5E7/5F4 tone control. I tried it out in TSC with a 38k source impedance and it behaved a lot differently. Who knows, that could be to your liking...

Just thought I'd throw that out there!

- Scott

[Bruce / Mission Amps]

Christ all mighty, don't mod that thing!
Just do something dumb like, sell the best small box, Fender reverb amp they ever came up with and build yourself a cheap tweed Deluxe clone... there are so MANY vendors out there selling Deluxe kits that you'd have zero trouble finding one.

[Bluefinger]

No, no, no ... I think you misunderstood something ... I don't have a PR that I want to mod. I want to build something from scratch again and neither a stock BF PR nor a tweed Deluxe are what I want to have. It's go to have reverb, bias tremolo would be nice, it should be rather compact but quite loud and efficient. The PR is a great amp, I agree but I am not into blackface type of sounds at all. It needs to be more old school. Yet my Tweed deluxe is too compressed for my taste, even after a couple of mods (rectifyer, fixed bias, filtering, ...). It might be a stupid idea to start with a PR if I want a tweed sound but since it does so many other things I am looking for, I considered this an option.

I also considered starting with something like a 5F4 (my all time favorite amp), put it in a 1x12 cab, give up the bias trem idea and add reverb. There are some schematics that can be found on the web but I wonder which one would work best in a 5F4. Most generic reverb circuits seem to be intended for bassmans so I wonder if they would work with a 5F4 and where I should put the reverb if I don't convert it to a long tailed PI (in front of V3 or even in between the two halfs of V3) ... but that's probably a different topic ...

thx

[Bruce / Mission Amps]

Ahh... OK then build a tweed 5E5 Pro, at around 25 watts with 6L6s-Kt66s-(etc), but with a 12" speaker cabinet and use an extra preamp tube, like a 6BM8 or 12DW7.
Then direct drive a high zed input reverb tank +2500 ohms), recovered from the same tube's other triode... into a pot for level.
Then mix the dry signal with the wet one across a few hundred thousand ohms before the predriver triode that drives the phase inverter.
Then use what ever FET or tube configuration you want to modulate the grid loads on the power tubes for "bias shift
vibrato.
Should be rather simple and the single tube reverb is usually more then enough reverb for most players.

[Bluefinger]

I have just compared the 5F4/5E5 schematic with the Princeton ... they both have the same type of PI with a predriver. So, shouldn't the Princeton reverb circuit work as well? This would be my first amp with reverb so I'd prefer to use an existing circuit for a start ... to be honest I don't have the necessary knowledge yet to turn your description into a working circuit. I would have another triode left for the trem so I could use the princeton tremolo circuit as well ... would you think that this is a bad idea?

thanks a lot

[Bruce / Mission Amps]

Well, this thread has gone all over the place.... what exactly do you want? A tweed Fender, a brown Fender, a BF Fender or ???
Tweaker-builders who think they can get one amp to do it all, frequently end up with an amp the does everything equally poor or at best, mundanely.
So, for a start, if you want the amp to sound a little more tweedish, then cathode bias the power tubes at around 10-11 watts each and put a bypass switch over the 250pF treble cap that engages a 1000pF to 1500pF cap in parallel and shunt some of the signal to ground with as resistor at the volume pot end of the cap.

[Bluefinger]

Yeah, I know, my thoughts are jumping all over the place ... I know what I want but I am not sure where to start ... should I take an amp that does the things I'd like it do do (Princeton) and tweak the sound or should I take an amp that sounds the way I want it to and try to teach it some new tricks (reverb, trem) ... I think I will probably stick with my original idea and try the Princeton approach. Since it's my first reverb amp I will build something that is a known working combination and then I can tweak the voicing a bit using the suggestions you made. One step at a time. The only thing for sure is that this will not be my last build so I might try the other route next time ...

thanks ...

[riz]

My .02, sounds like you might like a brown Fender, with reverb... I'm just getting into the brown amps, and I've gotta say, the descriptions I've read of them being between tweeds and blacks, with some characteristics of both, actually is pretty accurate--although I do feel they have a quality of their own. Really interesting sound, more "lush" than a blackface. Kind of mellow and aggressive at the same time, and hard to explain... I'm basing all this off an experience with one brown Concert, so take that into account.

[cminor9]

My .02, sounds like you might like a brown Fender, with reverb... I'm just getting into the brown amps, and I've gotta say, the descriptions I've read of them being between tweeds and blacks, with some characteristics of both, actually is pretty accurate--although I do feel they have a quality of their own. Really interesting sound, more "lush" than a blackface. Kind of mellow and aggressive at the same time, and hard to explain... I'm basing all this off an experience with one brown Concert, so take that into account.

to make it even more hard to explain, I have built a tweed deluxe, a brown deluxe, and a blackface deluxe reverb. I love the tweed, love the blackface, and hated the brownface. I was gonna scrap it until someone bought it.

Go figure.

[riz]

Ha-ha, actually, my first brownface experience was a Bandmaster that just sounded flat. Got it cheap, and it's been loaned out indefinitely--I'm thinking now I need to get it back and bias it with proper 5881 (I even thought of trying JJ 6v6 in it) because this Concert really sounds the business. Maybe I'm coming around to the brown thing. It seems like it's made for guitar>cord>amp kind of music! Doesn't like my fuzz-boxes, but a tubescreamer is nice.