Princeton Reverb build with no tremolo question

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Hi Gang,
I am trying to lay out a Princeton Reverb circuit without the tremolo and was wondering; Could I use the extra 12ax7 triode on the first preamp tube as a boost (kind of like jumping the 5e3 inputs)? So basically, move the tone stack recovery triode to the tube used for reverb recovery and use the 1st tube second triode for the boost. I would put in an additional 100k plate resistor and use a 25uf/1.5k bias circuit same as the first triode and then put a switch in place of input 2 on the front panel to jumper in the second triode. Would this work?

Thanks,
Tim

[Chuck H]

Can you provide a schematic of your idea? I always draw a schematic of any idea so I can look it over in the flesh before building.

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[Chuck H]

Thanks for providing the circuit diagram. A little tougher to analyze than a schematic, but it works out ok.

I'm not sure that circuit is going to give you much. First, what do you mean by "stack" then. You want channels in parallel? To me it looks like you've effectively paralleled the channels, but the "stacked" channel only doubles the number of triodes feeding the treble pot. I don't think that's going to be much boost. Not much instant gratification. Parallel triodes don't really boost output much, it lowers impedance. That's not a very dramatic change and probably less so through the treble cap only. Further, the way it's wired, with the "boost" off you have a 250p cap bleeding through a 100k plate resistor. That will effectively bleed high end a little in normal, un boosted operation.

What is your end goal? Do you want a "distortion" channel? A little clean boost? A treble boost? There are a lot of ways to use an extra triode. Series would be the most dramatic. Full parallel could be done a little differently for less gain than series, but more drama than the design you have now. What do you want it to sound like?

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Hey Chuck thanks for the reply. I am just looking for a use for the extra triode since I am not adding a tremolo. I thought that adding it to the input would be the same as jumper-ing on a 5e3 or 5f6. Basically to give the amp more boost and more drive. How should I implement the triode to achieve this?

Thanks,
Tim

[Chuck H]

If you would like a "boost" and just a use for the extra triode I might consider using a LTP PI instead of a concertina. I don't perceive much advantage to paralleling the typical Fender BF preamp. so parallel triodes will only boost MAYBE 2dB. The lower impedance advantage by doubling the triodes is also swamped by the high loss and high impedance tone stack/volume arrangement. You could also "Wreck" the preamp by adding the extra triode AFTER the second gain stage. This greatly reduces any affect the tone stack has on actual frequency balance as the tone controls are pre clipping. So the tone controls end up being distortion character controls and the frequency balance is entirely up to the OT and speaker cabinet. You could put the gain stage in front of the normal input, but IMHE the BFish type topography doesn't boost all that nicely. My own amp has the extra triode after the normal preamp, like a Wreck. I like it. I also use an attenuator a lot. My tone stack is also voiced for controlling distortion. The more stock Fender values won't be as good for this. My first choice in the LTP PI.

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If I do the Long Tail Pair, should I just mimic the Deluxe Reverb values? I'm a cookie cutter builder ;-)

[Chuck H]

That will work great. Changing the PR from trem to LTP is actually a popular mod. You can probably look it up on line to see what people think before you commit.