Adding "Blackface mode" to an AC30?

[roseblood11]

Has anybody done something similar before?

I`m planning to build a 3-channel AC30, based on the Weber 6V30 layout.

But I´d like to add a switch that brings the Top Boost channel closer to a Fender Blackface sound. (Sure, it`s still EL84`s into a Celestion Blue...) This switch wouldn`t be used on stage, it just would be an interesting option for recording.

As I understand it, the following things should be switched, maybe with a rotary:
1.) Bigger coupling cap in the preamp
2.) Change tone stack center frequency (...and remove that weird connection that Vox copied from Gibson?)
3.) Add NFB
4.) Disconnect the Vibrato channel from the PI, because of 3.)

https://www.tedweber.com/media/kits/6v30_schem.jpg

1/2 are easy, but how should 3/4 look like?

[pdf64]

It's a lot to ask of one switch, but not impossible per se.
The big problem as I see it is cramming connections to all those circuits together, as AC30 tend to rather sensitive to lead dress.
I don't think the amp will sound the same, even if you manage to keep it stable and the ground loops under control.

[roseblood11]

It could be two switches. 1/2 at the front plate, 3/4 closer to the PI tube

[stratomaster]

If memory serves, what you're describing post-switch is similar to the Dr Z Maz amps. I didn't think he bothered with NFB and got a cool Fender-ish tone. Maybe try the low hanging fruit first.

[AlNewman]

The bright input is already close to a fender tone stack, minus the cathode follower.  If the cathode follower was switchable, and split the difference with the first stage coupling cap, with .022, it would probably be close.  The 47pf treble cap seems out of place, but it's maybe balanced with the 1M pot.  Kinda looks like a marshall type channel how it's set up.

Perhaps raise the voltage at the PI and use a 12AT7.

A switchable NFB is pretty easy to wire in, but probably not required to get close.