Extreme Eq Pot

[Dona]

Hello everybody!!!

Pleasure to meet you, i'm Francesco, a newbie pedal maker from italy... So, sorry for my English  

This is my question.

I Want to Mod my Fuzz Face Clone with an Eq Pot (Aka Tone Pot) but i want to make it Very cool...
I have a 100k pot, i want to make it able to isolate Bass frequencies when it's turn off (No Hi, no Mid, ONLY basses!) and to isolate high frequencies in the opposite position (No bass, no mid, only hi!).

Somebody can help me? usualy i use THIS scheme for my tone pots, can i just mod it?

Thank you!

[GibsonGM]

You could download Duncan's tone stack calculator, and check out how a Big Muff Pi tone control is set up. I think you could modify it to do what you want!  And it is easy to work with this tone control.   Warning - you will need to add a buffer, and a recovery stage (1 dual opamp, or 2 transistors - look up the schematic for the Big Muff to see how it's done.  It is easy and you'll learn much by doing this).    This seems like the easiest way to get what you want and still keep your circuit "HOT" (without losing a lot of signal to passive components).   

Welcome, your english is fine!   Here is the link to the program:

http://www.duncanamps.com/tsc/index.html

[deafbutpicky]

what Gibson said plus a little hint:

-set R2 to 47k, C2 to 4.7n
-then alter C1 and C2 in equal steps until you find your desired "break point"

you might omit the first buffer stage Gibson mentioned this way...

[Dona]

Thank you very mouch!!
My FF has a very high output... you think i need a recovery stage after that? Some examples?

[deafbutpicky]

A buffer at the end would be a good idea, else copy the last part of a big muff,
that's what your inital scheme is anyway, just without the recovery stage.

[GibsonGM]

A buffer at the end would be a good idea, else copy the last part of a big muff,
that's what your inital scheme is anyway, just without the recovery stage.

Yeah, that's what I was getting at....you  probably will need the recovery stage to bring the signal level back up (the BMP stack suffers a pretty hefty insertion loss...something like -8dB...unless you have about 2 volts to spare, I'd plan on adding that stage).   Try it on a breadboard and see, no harm to experiment!  You MAY be happy with the level, but I would not be.   Your pedal is HOT right now, but add that stack, and it may seem lame.   It's up to you.

At minimum, as Deaf suggests, you'll possibly want SOMETHING there to buffer, which is why I suggest the recovery stage, same as the BMP.  Same number of parts, no problem with in/out Z,  and you keep your signal level the same or even get more if you like - you can adjust the gain of this section to your liking.

Either way, try the BMP stack - it should do what you want it to.

[Dona]

Anyway... this is my final TSC work...

[duck_arse]

hey, gibson, look at the load resistor on ^ that ^ big muff tone control. I wonder what happens when that is reduced to ~750k. might need something like a fet buffer following.

[GibsonGM]

hey, gibson, look at the load resistor on ^ that ^ big muff tone control. I wonder what happens when that is reduced to ~750k. might need something like a fet buffer following.

+1.     Dona, it looks good!  But change the 2.2M resistor on the lower right side to about 20k and see what happens. That resistor simulates the input impedance of the next stage, and we know the FF has very low input impedance!  The insertion loss gets very bad, noise gets higher, high frequencies go away....all very bad.   

I would plan on having an output buffer:    guitar >>  FF >> tone stack >> buffer >>>  other effects or amp. 

It is very simple to make a FET buffer, as Duck Arse just suggested, or just copy the BMP recovery stage.   Your tone will be much better if you do!