Mad Professor The Simble

The Simble is a Mad Professor overdrive pedal, announced as a transparent overdrive pedal¹². Delicious Audio described it plainly as "a transparent and organic sounding pedal with wide dynamic range, Dumble amp in a box"³.

The idea behind the pedal is to recreate an authentic tube sound without compromising the tone of your amp and guitar¹. In other words, it is aimed at players who want the character of a Dumble-style overdrive channel added on top of their existing rig, rather than a pedal that stamps its own voice over everything.

What it does

As an overdrive, the Simble pushes your signal into warm, amp-like breakup rather than hard clipping⁴¹. Because it is voiced after the Dumble Overdrive Special, the sound it reaches for is the smooth, dynamic, touch-responsive overdrive those amplifiers are known for⁵. MusicRadar's launch coverage noted that the pedal is intended to keep the core tone of your guitar and amp intact while adding that tube-style character¹.

The pedal has four knobs, and each maps to one job in the signal path⁵:

Sensitivity is the gain control, but it works by controlling the amount of signal being fed into the overdrive stage¹. That is the same approach a Dumble-style amp uses, where the input level into the overdrive circuit, set partly by how hard you pick, determines how much breakup you hear. Back off your picking dynamics or the guitar's volume and the pedal cleans up; dig in and it drives harder.

Contour handles the overall tonal balance, while Accent dials in brightness and edge at the top end⁵. Between the two, a player can shape how present or rounded the overdrive sits without touching the amp.

The MK2 reissue

In 2025 Mad Professor reissued the pedal as the Simble MK2, described by Guitar Pedal X as "a reissued and improved Dumble Drive"⁴. It is a variant of the original Simble rather than a new design, and MusicRadar reported it as available as of June 2025⁴⁶. The MK2 keeps the same four-control layout, with Level for output, Sensitivity for gain and compression, Contour for tone with unity at noon, and Accent for brightness and edge⁴.

Where it came from

The Dumble inspiration places the Simble in a family of pedals that aim to capture the Overdrive Special sound. Gearnews included it in a roundup of Dumble-style drive pedals, where its four-knob control set and its take on that classic circuit were the reasons it earned its place⁵.

Related pedals in the range

Mad Professor expanded the Simble line beyond the original overdrive. The Simble Predriver is a separate product that boosts the signal and compresses it without a slow attack time, adding musical harmonic overtones⁷. In Pete Thorn's demo of the Predriver, he noted that it adds upper harmonics to the signal and also works as a buffer for your signal chain, with a simple on/off footswitch⁸. The Twimble is a further pedal in the Simble line⁷.

For players comparing Dumble-style options, That Pedal Show covered the Simble alongside other D-style pedals in one of its demos, a useful side-by-side of how this circuit sits against its rivals⁹.

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