Paraphrase PI resistor value?

[Diverted]

Hi,

A friend and I are working on a point to point Rickenbacker M11 based on the schematics below. Only change in ours is there is only one input channel, so half of the first 6SC7 is going unused.
The original schematic I found online was a little confusing as to nodes and connections, and the output stage wiring was odd too. I changed it around to try to make it clearer.
See any issues with my re-draw?

One other thing I'm wondering is about the resistor off the top 6v6 that runs to the PI grid and the 10K (the one in question is circled in red in the modified schematic). There was no resistor value marked on the original schematic. I tried to find other paraphrase circuits as a guide and the early Fender 5E3 deluxes come close, but are not the same. Any suggestions on what value to put here? Thank you for any critiques and suggestions!

Ted

[sluckey]

Look at the 5B6 Bassman…

     https://el34world.com/charts/Schematics/files/Fender/Fender_bassman_5b6_schem.pdf


Or 5B3 Deluxe...

     https://el34world.com/charts/Schematics/files/Fender/Fender_deluxe_5b3_schem.pdf

[jjasilli]

This should also give you a good idea how to proceed with finalizing the design:  http://www.valvewizard.co.uk/paraphase.html


Feed a signal into the amp and measure signal voltage in the main signal path vs. inverted signal voltage.  Maybe temporally use a pot wired as a variable resistor in place of the R in question, to dial in the proper R value to get balanced signal voltages.  Then replace the pot with a fixed R of close value; or combine 2 R's in series or parallel to get an exact, non-standard R value.


EDIT:  I would also suggest that Merlin's drawing of the circuit is much easier to follow.

[Diverted]

Thanks for the tips.
One question: Merlin's version of this schematic; any idea where to locate it?

[jjasilli]

Merlin's schematics are in the website shown in my Reply #2.


Also note sluckey's 5B3 schematic which feeds 6V6's, like your amp.  The Bassman 5G6 feeds 6L6's which require more drive voltage.  Also the 5B3 paraPI circuit has the shared K resistor topology (unlike the Bassman which uses separate K resistors).


Note that in both Fender schematics, the signal sourcing for the paraPI is obvious. Your drawing has so many lines around the paraPI and the preceding gain stage, that it tends to resemble the drawing of a Long Tail Pair, which is confusing.

[2deaf]

I took the liberty of drawing it out and the gain was right in there at 40.  You have a voltage divider with 10K for one of the resistors.  You need to drop the voltage down 40 times.  A couple of strokes on the calculator yielded 390K for the other resistor in the voltage divider.