Tone

Three pot, Bass Middle & Treble tone controls that are used on a 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. 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 theEVJ) 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”