will this circuit work?

[yunger]

i wanted a different preamp in channel 2 because i thought the ef86 preamp had too much gain.....don't i feel foolish.
so i need add a more impeded tone stack or change some other values to choke the circuit or just live with the original ef86 and be thankful for the gain of knowledge.
maybe i could use the triodes in that 12ax7 in parallel like chuck was talking about. would this paralleled single gain stage get me closer? does this solve the phase issue if channel 1&2 were jumpered?

[ETR]

You really won't have too much gain because the pot is in between the two stages and it can be adjusted to clean. With an EF86 you can't really do that. The 100 ohm grid stopper that I suggested making bigger before will help keep it clean too. The tone control is typical of some early Marshalls and Fenders.

[Chuck H]

maybe i could use the triodes in that 12ax7 in parallel like chuck was talking about. would this paralleled single gain stage get me closer? does this solve the phase issue if channel 1&2 were jumpered?

I don't think you'll have ENOUGH gain if you do that. At the most you may need to lift the bypass cap on the second triode stage. You may also have to increase the value of the .0033 cap in the tone stack to get a usable range. But what you have is pretty good, and very tweakable. So you'll have plenty of adjustment room for dialing it in.

Chuck

[yunger]

after alot of research, i think i've decided to try a simpler circuit for my first build. i modified the preamp based on lots of reading and comments i've recieved here. hopefully i'm within a realistic, tweakable range. time to order parts!!
please feel free to comment if something sticks out.

[Bruce / Mission Amps]

after alot of research, i think i've decided to try a simpler circuit for my first build. i modified the preamp based on lots of reading and comments i've recieved here. hopefully i'm within a realistic, tweakable range. time to order parts!!
please feel free to comment if something sticks out.

How did you come up with or where did you get the values in that tone circuit?

[yunger]

well, i liked the teeter-totter effect of the big muff tone control on the duncan simulation as opposed to just a treble cut. i didn't think i would like the shelving of frequencies though and the source impedance was much lower in that circuit. i just started playing with it in a spice simulation. the values i used were chosen assuming 38k impedance. i found that, in combination with those values, the .022 coupling cap in front of the stack added a third dimention to the control. according to the bode plot, the lows now roll off instead of shelving. when the control is wide open, low end doesn't completely dissapear but drop to -14db under highs. over all, the control is pretty close to the marshall tone stack within the levels that i would use it...that is on paper.
seems like what i'm looking for since i don't have room for a "real" tone stack.