Adding a mids knob to a big muff pi

[ReeceAblaze]

Hello guys I wanna add a mids control to my big muff but I dont know what I need to change or where to buy components from?

[antonis]

A mids-unscooped Big Muff shouldn't be considered as Big Muff anymore..!! 

Anyway, adding a mids control should be more tricky than replacing original tonestack with a 3 band tone control, like Fender or Vox style..

[ReeceAblaze]

What I really wanted to do is if possible make a mid control knob for the big muff and have it activated and deactivated by a switch

[antonis]

What I'm trying to tell you is that Big Muff tonestack, as it is, exibits an "interaction" between HP & LP filters settings..
(the - famous for some guys, notorious for some other - 1kHz scoop..!!)
The above means that the existing tone control isn't able to achieve a flat responce..

By just adding a passive RC filter without altering existing LP & HP items values you can't have any mids control..
(you can't passively recover something lost..) 

[ReeceAblaze]

So its not doable at All?

[Mark Hammer]

You can't add a mids "control", but you can certainly increase the mids.  I modded a late '90s BMP by replacing the cap to ground on the "bass" side of the tonestack with one half its value, and installling a toggle to add a second cap in parallel to restore the original value.  With the smaller cap value, mids are retained when the Tone control is rotated to full bass.  How much mids is a function of the cap value you've selected.

[amz-fx]

AMZ Presence Control:

http://www.muzique.com/lab/tone3.htm

Best regards, Jack

[Suicufnoc]

Jacks got it. Not only possible, but quite easy!

[antonis]

Jacks got it. Not only possible, but quite easy!

If you only pay close attention on Jack's comments.. 
(like altering existing items values, resulting in altering original Tone control responce when Mids control disengaged and about driver source impedance..)

Not to be misunderstood..!! 

[Kennt82]

I put this together using some drawings from Kitrae's site.  Jack's AMZ, as you can see on the Hoof, works well.

[blackieNYC]

+1 on the AMZ

[ReeceAblaze]

How would I go about doing it I'm new to modding

[antonis]

For permanent engagement:
1. Get a schematic (diagram) of your specific version of Big Muff..
2. Trace on your board Tonestack placement..
3. Verify relative items & their values..
(C9/R5 & C8/R8 on first left Kitrae's tonestacks posted..)
4. Replace 22k (R5) with 2k2 only soldering one leg to GND..
5. Connect the other leg to lug 1 AND 2 of extra pot..
(R27 on Hoof..)
6. Connect pot's lug 3 to the node where R5 was initially placed..
7. Pray.. (optional but strongly recommended)

For switching mode:
1,2 & 3 as above..
4. Lift the other of grounded R5 (22k) leg and solder one of new R5 (2k2) on the grouded leg of 22k..
5. As above..
6. Connect pot's lug 3 to one side lug of a SPDT switch..
7. Connect original R5 (22k) free leg  to the other side of SPDT switch..
8. Connect middle lug of SPDT switch to to the node where original R5 (22k) was initially placed..
9. Pray.. (compulsorily)

[ReeceAblaze]

Do you know where I could get the parts needed ?

[pinkjimiphoton]

just make r5, the 22k in the tonestack a 50k linear pot wired as a variable resistor. let you cut or boost the mids. easy breezy.