Marshall Cab Sim

If I remember correctly this circuit is taken from original Marshall amp which has speaker simulator built in and it should provide frequency response similar to Marshall 4×12″ cab. It can be handy for direct amp-less recording or used in conjunction with Line Out from amp. Below is frequency plot of this circuit.

Marshall Speaker Sim frequency response


Click here to download schematic and PCB layout.


Click on a photo to see more details

26 Responses to “Marshall Cab Sim”
  1. Cabinet says:

    Hello I am wondering what is the must important part in the frequency we have to achieve in frequency respond

    • Bancika says:

      Every speaker sim needs a high and low frequency cutoff. Marshall also has a characteristic mid scoop that gives itthat dryer, more aggressive sound. This speaker sim tries to achieve all three aspects od eq shaping.

  2. Anjang says:

    i try to change resistor in input… but is still low…. somebody have idea what parts i changes for more bigger output ?

    • Delisys says:

      I built this today ,too.
      But I had no problem like you.
      Output was louder than bypass.

  3. Anjang says:

    i try this schematic already…. but this schematic output is too small, is very different with bypass… any idea what prats i change for more bigger output ?

  4. Robert says:

    Any sound or demo?

  5. Franko says:

    hi on the pcb what is the ov is that the ground for the 9v

  6. Ryan says:

    What is the total cost to build this, and does anyone have a list of all parts so I know what to get because I am new at this

  7. Graham says:

    I cant find a 2 nf capacitor anywhere. Could someone post a link please.

  8. Emilio says:

    Great pedal! Did you ever tried it also with acoustic guitar? If so, how is the sound?

  9. Rattler says:

    Hey man, this looks really sweet and I’m looking to build it but I can’t figure out from either of the diagrams where the LED goes in respect to the PCB… it’s probably just me being dumb but I can’t see it…

  10. Is the output sound clean? or with distortion?


    • Bancika says:

      It’s clean. This simulates only frequency response of a marshall 4×12. You’d need a bit more to simulate cone distortion.

  11. Robocell says:

    I have seen this circuit on another site and on it, there’s a clip

  12. Simen says:

    I want to build one of these, but I still lack some knowledge when it comes to op-amps.
    Most pedals out there use negative tip 9V power supplies, so I experimented in a Circuit simulator with -9V, and my first thought was to just flip all polarities, what goes to Op-Amp In- moved to Op-Amp In+ etc. but that didn’t work as expected. So I tried flipping the Op-Amp inputs one pair at a time, ending up at the exact same configuration as in the schematic, only difference actually being the power supply being -9V instead of +9V (and the output signal having a negative DC offset instead of positive). Is this correct? Is there anything else I must consider?

    Short version – Do I need to make any changes to the design/layout to use -9V instead of +9V?

    • Bancika says:

      I’m an op-amp noob myself, so can’t help much. I just built the +9V version according to the schem.

    • gillian says:

      I guess you confusing negative center of the DC jack with -9V, I didn’t saw pedal with “-9V”, except those positive grounded Germanium fuzz pedals, like the Fuzz Face or so.

  13. Tom says:

    How does this speaker simulator sound? Do you have any clips of it?

  14. Snowstorm says:

    I’m interested in this DIY cab simulator. But I can’t see any visible schematic, circuit or component list. Could you help me?
    Thank you for your collaboration.

    • Bancika says:

      Hi there, there is a schematic and layout in “Useful links” section of the article.

  15. Bancika says:

    Capacitors in pF range are mica or ceramic, nF range are box film caps and uF range are electrolytics

  16. claudito says:

    Concerning capacitors, witch ones are film, etc…

    Thank you

  17. vitor says:

    so, can you list all the components needed?

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    The idea behind this site is to share my experience with Do It Yourself approach to guitars, amplifiers and pedals. Whether you want to save a couple of bucks by performing a mod or upgrade yourself instead of paying a tech, or want to build your own piece of gear from scratch, I'm sure you will find something interesting here. Also, this is the home of DIY Layout Creator, a free piece of software for drawing circuit layouts and schematics, written with DIY enthusiasts in mind.