Op-amp overdrive with two clipping voicings and a clean bass blend, 2022 style

Pedal and tube amp circuits, solved part by part the way SPICE (the circuit simulator engineers use) does it, while you listen and watch. Turn the knobs, change any part, or tap a wire to put a probe on it.

How to use the bench

Every part is simulated. Nothing you hear is a recording.

  1. 1Pick a circuit

    Choose one from the menu, or type a name, maker or year in Find a circuit. The buttons under the menu switch between versions.

  2. 2Set the knobs and the input

    Turn the circuit’s knobs on the front panel. In the Input box, choose Guitar or Signal generator, and the note or chord.

  3. 3Press Play

    Press Play through the circuit to hear a picked note or chord. Play the string is the guitar by itself.

  4. 4Tap a part

    Tap any part on the schematic to change its value, or swap the transistor, tube or diode. The red numbers are DC voltages, and they update as you go.

  5. 5Tap a wire

    Tap a wire to put the probe there. The Probe graph and the spectrum show the signal there.

  6. 6Try a change

    Press Try it on a card under Try this to hear one change, before and after. Modify this circuit, below the schematic, adds or removes parts.

Good to know

Modeled after the Maestro Ranger Overdrive.

One gain stage feeds three inverting stages: a clean one that keeps only the bass, and two with diodes in their feedback. The Mode switch picks the first clipper mixed with the clean bass, or the second clipper alone.

Input

Add

Peak voltage from the pickup for each note. Strum hard and a single coil puts out a few hundred millivolts. When you play a chord, its strings share this level.

How it’s played
Tap a part to change its value, or a wire to probe it. To add or take out parts, open Modify this circuit, below. Red numbers are DC voltages to ground, not warnings. Scroll or drag sideways to see the whole circuit.
Modify this circuit Add parts, take them out, or put one in series with another, then hear what it does. Tap to open.

Pick what to do, then tap the schematic. Your changes show in purple. Any change can go on a switch beside the knobs, from the menu in its row under Your changes.

Add a part

Tap where each leg goes. Tap both ends of a part to put the new one across that part.

Change a part

With Remove a part on, tap any part of the pedal or amp to take it out, and tap it again to put it back. Tapping a purple part you added deletes it.

Turn on Add in series with a leg and tap a part. In that part’s box, below the schematic, pick which leg to lift and what goes in the gap, such as a resistor between a cap and ground or a stopper in front of a grid.

Change a wire

With Cut into a wire on, tap any wire. Pick a part from the menu and it goes in the gap, wired in. Volume pot puts a pot there with the input on one end, the output on the wiper and the other end to ground.

With Run a wire on, tap a leg, then where the wire goes. Drag any piece of a wire you ran, or of an added part’s lead, to square it up or move it.

Keep and share

Your changes stay in this browser, on this device, for your next visit. Nothing is sent to us. Anyone using this browser can see them. They’re lost if you clear your browsing data or use a private window, so save a file to keep a copy. A shared link carries the circuit after the #, a part browsers never send to a server.

Test tone for the graphs
The graphs use a steady tone. Play sounds a plucked string that dies away.

Input

pickup, unloadedat the pedal input

Output

at the amp input

Probe

Spectrum

Frequency response

What the curves mean

The ink curve is the response to a very quiet signal, from the generator to the probe. The blue curve is measured with pink noise at the level you set, like an audio analyzer. When stages clip, the blue curve pulls away from the ink one and the gray coherence line (right-hand scale) drops below 1. Then no single curve tells the whole story. Both use the signal generator, whichever Input tab is picked.

Output

Bias

every voltage and current at rest

What to listen for. IC1.1 is the gain stage. Gain moves its wiper along the pot, so more of the pot is in the feedback and less in the way out: the gain runs from about one to about 7 at 1 kHz, more in the treble. Below about 300 Hz C3 brings it back toward one. Three inverting stages take that signal. IC1.2 is clean and keeps only the bass, below about 160 Hz. IC2.1 and IC2.2 each have two diodes in series each way across part of their feedback, with a resistor in series, so they clip softly. The Mode switch picks IC2.1 mixed with the clean bass in IC3.1, or IC2.2 on its own.

Download.

Parts and what they do

Stock values. Tap a part on the schematic to change it.

R100, 49.9 kΩ
Top of the Vref divider.
R101, 49.9 kΩ
Bottom of the Vref divider.
C103, 22 µF electrolytic
Filters Vref.
R1, 1 MΩ
From the input to ground.
C1, 10 nF
Input coupling cap. Against R4 it trims below about 16 Hz.
R4, 1 MΩ
Holds the plus input at Vref.
IC1.1, JRC4558D
The gain stage, non-inverting.
Gain, 100 kΩ pot, reverse audio taper
Gain, a 100 kΩ reverse-audio pot, its wiper on the op-amp’s output. Turned up, more of it is in the feedback and less between the output and G, so the gain rises.
R5, 10 kΩ
Least feedback resistance.
C4, 100 pF
Across R5.
R3, 24.9 kΩ
Gain leg: 24.9 kΩ to the cap to Vref.
R2, 34.8 kΩ
Gain leg: 34.8 kΩ with C2, in parallel with R3, so the treble gets more gain.
C2, 10 nF
In series with R2.
C3, 22 nF
In series with the gain leg, so the gain falls toward one in the bass, below about 300 Hz.
C7, 1 µF electrolytic
Into the clean stage.
R7, 10 kΩ
Clean stage input resistor.
IC1.2, JRC4558D
The clean stage, inverting, a gain of one in the bass.
R13, 10 kΩ
Clean stage feedback.
C10, 100 nF
Across R13, so the clean stage rolls off above about 160 Hz: only the bass gets through.
C13, 1 µF electrolytic
Clean path into the mixer.
R16, 10 kΩ
Mixing resistor, clean path.
C6, 1 µF electrolytic
Into the first clipper.
R6, 10 kΩ
First clipper input resistor.
IC2.1, JRC4558D
The first clipper, inverting, a gain of about 9 before the diodes.
R11, 90.9 kΩ
First clipper feedback resistor.
C8, 100 pF
Across the feedback.
R9, 6.04 kΩ
In series with the diodes. Once they conduct, the gain drops toward 6.04 k over 10 k, so the clipping is soft.
D1, D2, D5, D6, 2 × 1N914 / 1N4148, one each way
Two 1N4148s in series each way.
C11, 1 µF electrolytic
First clipper into the mixer.
R14, 10 kΩ
Mixing resistor, first clipper.
IC3.1, JRC4558D
The mixer, inverting, a gain of about 1.6 for each path.
R18, 15.8 kΩ
Mixer feedback.
C15, 6.8 nF
Across R18. It rolls off above about 1.5 kHz.
C17, 1 µF electrolytic
Blend path output cap.
R20, 1 MΩ
Holds the blend path at ground for DC.
C5, 100 nF
Into the second clipper. Against R8 it cuts below about 160 Hz.
R8, 10 kΩ
Second clipper input resistor.
IC2.2, JRC4558D
The second clipper, inverting, a gain of about 22 before the diodes.
R12, 220 kΩ
Second clipper feedback resistor.
C9, 330 pF
Across the feedback. It rolls off above about 2.2 kHz.
R10, 7.68 kΩ
In series with the diodes.
D3, D4, D7, D8, 2 × 1N914 / 1N4148, one each way
Two 1N914s in series each way.
C12, 1 µF electrolytic
Into the second inverter.
R15, 10 kΩ
Second inverter input resistor.
IC3.2, JRC4558D
Inverts the second clipper back, a gain of about 2.2.
R17, 22.1 kΩ
Second inverter feedback.
C14, 6.8 nF
Across R17. It rolls off above about 1 kHz.
C16, 1 µF electrolytic
Second clipper path output cap.
R19, 1 MΩ
Holds the second path at ground for DC.
R21, 1 kΩ
Into the Tone control.
Tone, 25 kΩ pot, linear taper
Tone, a 25 kΩ linear pot with 18 nF from its bottom to ground. Turned down, more of the cap reaches the wiper and the treble drops.
C18, 18 nF
The treble cut cap.
Volume, 100 kΩ pot, linear taper
Volume, a 100 kΩ linear pot.

About this version

JRC4558D
Negative ground, 9 V. Six halves of three JRC4558D op-amps.

How this tool works. Every part is an equation, and the whole circuit is solved several times per audio sample: 192,000 samples a second while you drag a knob, 384,000 once you let go. Transistors use Ebers-Moll with gain, leakage, Early effect, base resistance, junction capacitance and temperature. Their charge storage is set at the bias point, close for small signals and rough while they switch hard. Tubes use Koren’s equations fitted to each datasheet, plus grid current. Diodes are exponential junctions with series resistance. Presets are typical of each type. Caps are ideal, and the battery or HT is a voltage behind a resistance.

Spot an error, or want a circuit added? Email info@swellamps.com. A schematic or a clear photo of one helps. Anything you send may be used to improve these models and our desktop app.

© 2026 Swell Amplification LLC. All rights reserved. The simulator, its circuit models, drawings, presets and text are the property of Swell Amplification LLC and may not be copied, reproduced, redistributed or used to build another product without written permission. The original circuits are historical designs documented in public sources, and no claim is made to them. Everything here is provided as is, without warranty of any kind, for study and personal use. Results are simulations of typical parts, not measurements of any real unit. Don’t rely on them for the safety of any build or repair. Tube amplifiers carry lethal voltages.

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