curious about blackface tone circuit on 4xEL84 amp

[luthierwnc]

Hi All,  Noodling with another build.  I was thinking about something along the HC30 line except swapping a blackface-style preamp for the 59-Bassman cathode follower.  The EF86 would stay the same.  This is in the wondering stage right now but I have a couple amps with the stack after the second preamp tube.  The phase would stay the same on the 12AX channel feeding into the opposite end of the inverter.  FWIW, the Divided by 13 schematics I've seen on their FTR 37 are similar except for using a quad of cathode-biased 6V6s. 

Just looking for random thoughts here.  Thanks, sh

[luthierwnc]

Got a PM to make myself understood.  Here is a link to the schematics of the /x13: https://el34world.com/Forum/index.php?topic=15506.0
I'm thinking simpler with the sharp-cutoff pentode more-or-less as shown but without the cathode follower - more along the lines of a Vox or Matchless.  13 uses a 5879 tube which I really like but it could be an EF86 for the same reason.  The lower circuit is your garden-variety blackface.  That has another gain stage going into the PI after recovering from the reverb circuit that I'd likely eliminate.  That keeps the phases opposite going into either end of the  PI tube.
The only real difference between these and the Matchless 30 circuits is the lower side is six years newer.  I've already got a couple Bassman/Marshall amps but no blackfaces except a Dumble clone with the bells and whistles tamed.  Two preamp tubes, one for the PI and then power tubes and rectifier.  My experience with EL84 amps is that they don't like more than 350VDC on the plates.  You can do it but they sound a bit harsh.  You don't want the filtration too stiff either. 

FWIW, thanks, sh 

[pdf64]

Don’t overlook the admittedly short lived (4 months!) 6G9 tremolux https://el34world.com/charts/Schematics/files/Fender/Fender_tremolux_6g9.pdf
Brown era tone stacks are pretty close to Black.

[luthierwnc]

Thanks PDF64!


One of my most recent projects was a 6G3 with a slightly more British second channel.  That is definitely a keeper but I think it scratches the itch for that era amp.  sh

[luthierwnc]

PDF64  here is the circuit I'm contemplating.  The trimmer after the 12AX7 channel is there to not overwhelm the pentode channel.  sh