modding ROG Eighteen tone stack

[jogina111]

hi, I'm planning to mod the runoffgroove eighteen tone control to a TMB  tonestack.. Would it be possible? If so, how and where do I wire it? Should it go to the tone control's place or at the end of the circuit?
Help please...

[GibsonGM]

Hi,

It's not a bad idea to try modifying tone controls.  In fact, it's the nature of what we do!  To do this on the Eighteen, you would remove the existing tone control (the resistor and pot next to the tone control, and the 4.7n and 10n capacitors).   Then you would feed your new tone control (FMV?) from where the 4n7 cap currently is. 

Now - a TMB stack would suffer quite a bit of INSERTION LOSS.  That means they 'eat' your signal, making the signal level going to the following FET stage much lower than what it receives with the tone stack the way it is.  Actually, it loads the previous stage...it's an impedance issue.   In short, you might never be able to clip the signal, and it may be very noisy!   

Putting in a real TMB/FMV tone control may even mean having to add an additional gain stage (a 'recovery stage') to bring the signal back to a suitable level.  If you breadboard this, think about adding another gain stage.  You would be making a totally different pedal, in essence.    And be sure not to allow DC from your mods to flow into the signal path...currently the 10n cap at the 2nd gain stage gate is preventing that.

I would be more inclined to experiment with the values of the capacitors already there, honestly.  The guys at ROG played with the tone stack, and that is what worked for them!     But in the spirit of DIY, you CAN mess around with the stack, as long as you know that you might need to boost that signal afterwards.   Hope that explained, a little.
Good luck!

[GibsonGM]

They are talking about this a little here:  http://www.diystompboxes.com/smfforum/index.php?topic=102897.0

Very similar issue!