A Fender amp's treble, middle and bass knobs are just this
The passive tone stack behind a classic Fender amp's treble, middle and bass knobs: three pots, three caps and one resistor.
Free build sheet
The parts, every wire with its length and bend points, a bend guide, both sides of the board and checkboxes to track your progress. Print it or keep it open at the bench.
Open the build sheetWhat you need
9 parts on a perfboard 16 × 27 holes, plus hookup wire.
| Qty | Part | Where to buy |
|---|---|---|
| 1 | Ceramic Cap250pF C1 | Buy Ceramic Cap on Amazon |
| 2 | Ceramic Cap20nF C2, C3 | Buy Ceramic Cap on Amazon |
| 2 | Screw Terminal 2P (5.08mm) J1, J2 | |
| 3 | Potentiometer Q1, Q2, Q3 | |
| 1 | Resistor (axial)56k R1 | Buy Resistor (axial) on Amazon |
Check every pin against the datasheet of the exact part in your hands before wiring.
As an Amazon Associate I earn from qualifying purchases.
Cut list
9 wires, 242 mm (9.5 in) in total, in the order the build sheet cuts them. Wire numbers match the build sheet. Each length includes 5 mm per end to go through the hole.
| Wire | Colour and net | Length | ||
|---|---|---|---|---|
| 6 | BlackSLOPE L12 → L19 | L12 → L19 | 28mm | Straight |
| 5 | BlueSLOPE M13 → K13 | M13 → K13 | 15mm | Straight |
| 4 | GreenIN J7 → H5 | J7 → H5 | 20mm | 10mm (90°) |
| 1 | RedMIDCAP L20 → H20 | L20 → H20 | 20mm | Straight |
| 7 | RedOUT I10 → D22 | I10 → D22 | 53mm | 18mm (90°) |
| 3 | WhiteBASS I14 → H12 | I14 → H12 | 18mm | 10mm (90°) |
| 9 | WhiteGND G18 → K4 | G18 → K4 | 56mm | 41mm (90°) |
| 2 | YellowBASS J15 → H15 | J15 → H15 | 15mm | Straight |
| 8 | YellowGND G20 → G23 | G20 → G23 | 18mm | Straight |
About this build
The treble, middle and bass knobs on a classic Fender amp are a passive tone stack: three pots, three caps and one resistor. I used the values from the 1959 Fender Bassman 5F6-A schematic: a 250pF treble cap, two 20nF caps, a 56k slope resistor, and 250k treble, 1M bass and 25k middle pots. Marshall copied the same circuit for its first amp, the JTM45.
The signal comes in on one screw terminal and leaves on the other. Nothing here amplifies. The stack only cuts, and the three knobs decide which frequencies get cut the most. The pot footprint uses generic numbered terminals, so find the wiper on your own pot's datasheet before wiring it.
Safety: in the Bassman this stack is driven straight from a tube stage, and its caps sit at a high DC voltage. This board is drawn for a buffered, low voltage build. Never treat a tube amp's tone stack as low voltage, and check that amp's own schematic before you touch one.
Fender, Bassman, Marshall and JTM45 are trademarks of their owners. This is a recreation from the published schematic values, and PerfBoard is not affiliated with or endorsed by Fender or Marshall.
More builds
See all builds
VideoThe fuzz pedal Jimi Hendrix played
A recreation of the Fuzz Face, the two transistor fuzz pedal Jimi Hendrix played, with fuzz and volume knobs.
14 parts · 18 wires
Guitar and audio
VideoThe amplifier inside a million kit speakers
The LM386 minimum parts amplifier, the chip inside countless kit speakers, with a volume knob and a terminal for a small speaker.
10 parts · 17 wires
Guitar and audio
VideoThe two-knob synth from 1980 still sounds like a broken robot
A two knob noise box from a pair of 555 timers. It makes the stepped, gritty square wave tone people have built since 1980.
11 parts · 17 wires
Guitar and audioGames and toys