Slightly Technical

Tools · Free

Tone Stack Lab

Turn a real amp's tone controls and watch the frequency response move — then hear it. 55 sets of component values across 15 circuit families, 39 of them traced from factory schematics.

A tone stack is three or four parts and a great deal of folklore. The parts are simple enough to solve exactly; the folklore is what happens when nobody does. This solves the actual circuit — a full nodal analysis of the netlist, not a stored curve — so switching a cap or a pot taper moves the plot the way it would move the amp.

The presets are the useful part. A "Marshall tone stack" is not one circuit: a JTM45, a 1959 Super Lead, a JCM800 and an SLO-100 share a topology and disagree about almost every value in it. Those differences are most of what people mean when they say those amps sound different, and you can put them side by side here.

The library

55 presets across 15 families

39 of them were traced from a factory schematic rather than taken from the values everyone repeats. Pick one to open it in the lab.

Amps

FMV (Fender / Marshall / Vox)

James / Baxandall

Dumble ODS

Tweed E-Series

Aria (bass amp)

Hiwatt DR

Pedals

Big Muff tone

Tilt EQ

Fuzz Face loading

Rangemaster input

RAT filter

Tube Screamer tone

Guitar & misc

Bridged-T notch

Cab-sim LPF

Varitone

Reading the plot

Three things the curve tells you

The mid control is a scoop, not a boost

On a Fender or Marshall stack, the whole curve sits below unity and the controls only decide how far below. Turning the mid down does not cut a band out of a flat response — it deepens a notch that is always there. Watch the level scale, not just the shape.

Every control moves every other one

The three pots in an FMV stack share the same node, so bass and treble both drag the mid notch around with them. This is why the same settings sound different on two amps with the same circuit but different component values — and why A/B-ing two pinned curves tells you more than reading one.

What drives the stack changes the stack

A cathode follower and a plate-driven stage do not present the same source impedance, and the stack loads differently as a result. The source and load panels are not decoration — switching driver type visibly moves the curve, which is a large part of why a 5F6-A and a JTM45 are not the same amp.

Also on the bench

Setting the bias on the amp you just modelled

Change the tone stack and nothing about the output stage cares. Change a power tube and everything does. Bias Bench does that side of the arithmetic — fixed and cathode bias, push-pull and single-ended, screen current and PSU sag included.

Open Bias Bench →

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