Three pot, Bass Middle & Treble tone controls that are used on my Blackheart BH5.

From left to right the pots are Bass, Middle, Treble and Volume.
The signal comes in at the join where the 100k resistor and 470pf silver-mica capacitor meet.
The other end of the silver-mica capacitor joins the left pin(photo), top pin(schematic) of the treble pot.

The centre pin of the Treble pot is where the signal goes out to the volume pot,
The centre pin of the volume pot is where the signal goes out to the next stage.

The Black wires go to ground.
The other side of the 100k resistor goes to the two .022 capacitors,
The .022 capacitors connect to the bass and mid pots,
with the left and centre pins of the bass pot tied together.

This same circuit is shared by other amps with changes to only some of the part values. (highlighted in red)

Blackheart BH5 

C2 - 470pf
C3 - .022uf
C4 - .022uf
R5 - 100k
Treb - B250k
Bass - A1M
Mid - B25k
Marshall Plexi 

C2 - 470pf
C3 - .022uf
C4 - .022uf
R5 - 33k
Treb - B250k
Bass - A1M
Mid - B25k
Mesa boogie
V-Twin
C2 - 500pf
C3 - .022uf
C4 - .022uf
R5 - 100k
Treb - B200k
Bass - A1M
Mid - B25k
Marshall Class 5 

C2 - 470pf
C3 - .047uf
C4 - .022uf
R5 - 68k
Treb - B200k
Bass - A1M
Mid - B20k
Slightly different circuit shared by Fender Twin and other amps with changes to the part values. (highlighted in red)
Fender Twin 

C2 - 250pf
C3 - .1uf
C4 - .047uf
R5 - 100k
Treb - B250k
Bass - A1M
Mid - B10k
Fender
Blues Deluxe
C2 - 250pf
C3 - .1uf
C4 - .022uf
R5 - 100k
Treb - B250k
Bass - A1M
Mid - B25k
Mesa boogie
Lonestar
C2 - 250pf
C3 - .1uf
C4 - .047uf
R5 - 100k
Treb - B250k
Bass - B250k
Mid - B10k

Two pot, Bass & Treble tone controls
There are minor variations to the three pot tone circuit. Some leave out the Mid control, replacing it with a fixed resistor.

The Baxandall tone stack

Commonly found in hi-fi designs usually centred around a midrange frequency of 1KHz, while most guitar amp tone circuits are centred around a midrange frequency from 300hz to 500hz. With Fender-type stacks the bass and treble knobs mostly just boost, and the mids knob mostly just cuts. So in that case having all of the knobs at "noon" actually creates a scoop of the mids. They can't provide a true mid boost, they are used in many guitar amps because most guitarists prefer midrange cut, and don't need the apparent midrange boost the Baxandall provides. Many amp builders have used the Baxandall tone stack in guitar amps with pleasing results. The Baxandall tone stack is featured in Duncan Amp’s Tone Stack Calculator under the name “James”.

 


Single pot tone controls

Fender “Brownface”  treble cut cap .01uf    treble lift cap 500pF silver mica
Fender “Tweed”  treble cut cap .0047uf Sprague Orange Drop 715P   treble lift cap 500pF silver mica

Connect the left pin of vol pot to the middle pin of tone pot. Connect the silver mica capacitor from the middle pin of vol pot to the left pin of tone pot. Connect the .01uf capacitor from the right pin of the vol pot to the right pin of the tone pot, then from here to ground.

Marshall “Plexi” treble cut cap .01uf  treble lift cap 500pF silver mica

The centre pin of the volume pot (red wire on the EVJ) is where the signal goes out to the next stage. Connect the centre pin of volume pot to the centre pin of tone pot. The left pin of the volume pot (white wire on the EVJ) is where the signal comes in. Connect the silver mica capacitor from the left pin of tone pot to the left pin of volume pot. Connect the .01uf capacitor from the right pin of the tone pot to the right pin of the volume pot, then from here to ground (black wire on the EVJ).

 

Marshall “18 Watt”