switching between tone controls

[EETStudent]

I have a Fender clone and a Silvertone 1484 tone stack that I want to incorporate into it. Both tone stacks sound different, and i was wanting to add a switch that can toggle between the two. When I tried it, it worked somewhat successfully and I think I know why. Both stacks fed into the grid of the next stage. Both master volumes worked on either setting, and I think this was because the signal was bleeding back through and affecting( in a negative way) both controls at the same time. So, is there a way I can wire the switch to totally isolate both tone controls without having to relocate them? Should they share a master volume?

[Tubis]

You will have to use a two pole switch so you can switch before and after the tonestack.

If you have a cathode follower before you can switch only after the tonestacks but if you drive theme from the plate they will load down some frequencies

And offcourse they will bleed backwards after the stacks.
The higher the other master is set the more it will bleed and if you use a single master it will bleed the most.
I would switch before and after the stacks if you drive from the plate and only after if you drive from the cathode.

[Rob Mercure]

ES,

Are you familiar with "Duncan's Tube Amp Pages?" Goggle to find 'em and down load the tone control simulator and 'go to town." The 1484, as best I remember uses a type or Edwards/Baxandahl tone stack go get you started. This should provide you with the tools to cobble up your circuit.

Rob

[Don Moose]

I think the switching approach you want here is to leave the two tone stacks connected to the driving stage, but disconnect each stack's MV wiper and its connection to GND at the same time.

A DPDT setup should do it.

[EETStudent]

Rob, I am familiar with Duncans tone stack calculator, which was a help in fine tuning my fender stack. I copied the silvertone circuit straight off the 1484 schematic. Both stacks are complete, Im just working on interchanging them.

[EETStudent]

Don, your idea sounds good. Im trying to wrap my brain around that concept, but i cant seem to quite get it. You say disconnect MV wipers(path to grid) and disconnect grounds accordingly as well. The only thing i can think of is to send two wires from the grid of the following stage to the two middle terminals on the switch, since both master volumes have that in common. Wire the top left terminal to one master volume, and the bottom right to the other, effectively directing the signal accordingly. Now, what about ground? What am I doing wrong here?

[Tubis]

I think the switching approach you want here is to leave the two tone stacks connected to the driving stage, but disconnect each stack's MV wiper and its connection to GND at the same time.

A DPDT setup should do it.

What would disconnecting the ground be good for?
If you disconnect the input of the MV and ground i could see the reason but not the wiper and ground. There usualy is smaller resistanses going to ground in the tonestack that will affect the over stack far more than the MV wich usualy is 1M.

[Steve Conner]

Yes, so I imagine Don meant to disconnect the ground connection of the entire tonestack/MV assembly. When making an amp, you (well I) usually wire the bass, treble and volume pots together with the tone stack components into a single unit with an input wire, an output wire and a ground wire. The input wire goes to the plate (or cathode) of the driving stage via a coupling cap, and the output wire goes straight to the grid of the next stage. The ground wire goes guess where. :-P

But disconnecting the ground wire just amounts to the same thing as disconnecting the input of the tone stack from the previous stage, so I'd recommend doing that instead, as it's easier to understand.

So basically use a DPDT switch to swap the input and output wires of your two tonestack modules onto the plate and grid of the relevant tubes.

[Don Moose]

Right - ungrounding that ground connection effectively disables the affected tone stack. For some stupid reason I believe that doing it this way will make for a smaller pop problem to solve.

You still need a grid-to-gnd resistor (something big 10M or so) ... at least I would ... on the follwing stage.

Well - whatever works.