After unsuccessful attempts to add a presence circuit to a circuit similar to that of a Princeton Reverb I had thought of adding a preamp step with gain 1 and unbypassed cathode to apply feedback there with an effective presence circuit. It is the added gray area (not yet determined). It is taken from the Super Amp 5F4.

https://el34world.com/charts/Schemat..._super_5f4.pdf

How could it be built? The interest is in obtaining a preamp step with gain 1 and that does not alter the contours of the previous circuit. It can be a useful resource for this and other purposes.

In orange, the Princeton circuit.

In gray, the preamp step added.

One of the resources to attenuate the extra amplification starting from a traditional 100K plate / 1K5 cathode circuit could be a split anode resistor but I don't know how I could compose the previous voltage divider to get closer to that idea. I have put values by eye in the voltage divider (2M2 and 470K) but I do not know how to calculate the set mathematically to at least find an approximation.

Thanks to all!

https://el34world.com/charts/Schemat..._super_5f4.pdf

How could it be built? The interest is in obtaining a preamp step with gain 1 and that does not alter the contours of the previous circuit. It can be a useful resource for this and other purposes.

In orange, the Princeton circuit.

In gray, the preamp step added.

One of the resources to attenuate the extra amplification starting from a traditional 100K plate / 1K5 cathode circuit could be a split anode resistor but I don't know how I could compose the previous voltage divider to get closer to that idea. I have put values by eye in the voltage divider (2M2 and 470K) but I do not know how to calculate the set mathematically to at least find an approximation.

Thanks to all!

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